When reading this before, I was confused. “Why would someone trade guidance for misguidance? Especially some people the Quran explicitly mentions, the people that know the truth but choose to conceal it.” This time around, I’ve found my answer and now see that Muslims also often find it appealing to exchange guidance for misguidance. I paid closer attention to the sentence following the first one: “But this trade is profitless…” People trade belief for all sorts of profits because they completely disregard its worth. They betray themselves. Faith is an intrinsic gift, a vast gift that never stops giving, given to us since birth. The Fitrah. We who were even born Muslims struggle with temptations around us and at times even wish we could have the joy others have when sinning. Pleasure is a profit. Yet recently when I fell into that sort of mindset, I laughed at myself. I thought: “Am I really comparing the joy that Allah gives to the joy that sins give? Have disbelievers ever experienced weeping in prayer? Have they ever been greeted with peace? Do they have a purpose for their restraint and discipline? Have they ever had a mind filled with clarity? Do they love the Most Loving?” Once we flip it around, Islam is unmatched when it comes to profits even in the dunya. The people who left Islam likely never even tasted its worth in the first place, the essence of iman, but may Allah protect us. We ignore the One who is keeping us alive every second. The Sustainer of all. 
Profits make you feel good. The reward after so much striving is so temporarily fulfilling. Just know that if you become distressed by the pursuit for Islam and excellence, you’re doing something wrong. Allah intends to lighten for you. He is so merciful that He does what we like. “Do you not love to be forgiven by Allah?” He knows that we love to be forgiven and does it willingly. He assigns His names onto himself, He doesn’t need to forgive us, yet He does. This is our Lord. He forgives all, He loves purely, He laughs and He protects. So how could I not love Him? The One who designed me perfectly? All of us Muslims each have such an individual and unique relationship with Allah, He never tires of us until we tire of Him, and each of our relationships are certainly better than Atheists who reject any relationship entirely, so no matter what, smile at least at that. This verse also shows us that repentance ultimately eases us of our burdens. So again, if repentance sounds like the scariest thing on earth, then you need a major perspective shift. But we forget that Islam is something you have to chase, just as you have to chase any other fleeting profit in this world. You have to chase success. You have to chase joy (happiness is a skill). I look at what I often chase: validation, understanding, acceptance (on an individual and societal scale). I go to extreme lengths to achieve these things at times, so much so that I become distressed by them. You have to chase Islam and Islam never becomes distressing. You have to be vulnerable before Allah in prayer even if it feels uncomfortable. You need to pray your five daily prayers. You need to leave off suffocating sins. We can assume that Islam gives this crushing weight to sins, that we’d be enjoying them to the fullest if we simply disregarded Islam, yet the crush the heart feels never stops pressing down even after death. Just listen to the reverts. We often chase things that are exclusive, it’s human nature. Yet what is more exclusive than Allah? Allah is the highest profit, the One most worthy of our striving. So push yourself. Allah is Ash-Shakur. Whatever you’re chasing, you’ll find in Allah. He is Beauty. Your best, most majestic Wali. Friend. The profits of faith are infinite. Do you realise the scale of infinity? So once Islam is your priority, everything else seems like a silly game. Ibn al Qayyim (rahimahullah) says, “Indeed iman has a joy and sweetness in the heart. Whoever does not experience it either lacks or is deficient in his iman.” Indeed nothing compares to the sweetness of iman. Whoever tastes the profit of faith once, iman, although he may lose it, he will always yearn for it again.
 I recommend an article on lifewithallah.com: 
“Tasting the sweetness of Iman”

Julie Aoulad-Ali Ameen. Wa iyyak, barakAllahu feek! I‘m so glad this resonated with you, jazakAllahu khairan for leaving this comment.

Allah SWT clarified that what is real profit or success. It means not the wealth we have in our bank. Allah SWT says! Who dedicate everything in the way of Allah (Fi-sabi-lillah) yes, people can ask how dedicate everything in the way of Allah SWT. Dedicating does not mean you don't enjoy the blessings of Allah SWT no you enjoy, you are the user. You are given by Creator. In this modern world, we don't own money, money owns us, we don't own power, power owns us, we don't own status,status owns us. We became slave to worldly things and forgot "We all belong to Allah SWT and to Him we return". 
Yes, you enjoy but temporary. 
Let me say in clear statement:  "You attach with this world temporary as this world is attached with you temporary". You use this world temporary as this world is using you temporary". I say this because my own experiences in my personal life that "Pain is block between You and Dunya, pain is not letting you to attach with the temporary world and pain shows you the reality of the dunya,  that's why Allah SWT tests those to whom He loves because He SWT do not want to attach you with the temporary world, He exactly knows one day It will leave you alone."

Shara or bay3 is an exchange of goods, services , and can be with in kind items, not necessarily goods for money. Here they exchanged guidance for misguidance,  the most miserable trade anyone can make.

He compared the hypocrites to someone who lit a fire, and the only reason you would light a fire in darkness of the night  is for warmth, comfort, and to be able to see in the darkness around you. In that way belief grants you Serenity, warmth, and the ability to see through the darkness with the light of Allah. He then mentions that he took away their light and that is because they turned away from belief so he left them in darkness without the light that they once had. Now he did not say that he took away the fire (nar), he said he took away the light (noor) from the fire, so that would mean the smoke and the burning remained without the benefit of the light. And that is what happens when belief leaves a heart, heart becomes in a worse state then had it was in before accepting the belief in the first place, and that is because turning away from the truth after having it is worse then never having it at all. He then said they are blind, dumb, and deaf after having their light taken away, and someone in that state will not be able to relight the fire as he wont be able to find the wood and tools needed to light a fire in the wild. In that way the one who turns away from belief after having had it, will be blind deaf and mute to the signs that will guide him back to belief once again

It may please be noticed that for the effect of light caused by the FIRE, the word 'Adaat (Illuminated)' was used. However, for the thing that was taken away from the said persons, the word  'noor' was used. The 'illumination' created BY THE FIRE and the 'NOOR' taken away from the said persons may be two different things; one is the property of fire the other one is the capability of the persons.      
As I understand it, the word says that the light (noor) was taken away from the said persons; rather than from the fire.  So the fire may still be there with its properties/characteristics, that is heat(with negative connotation), with warmth (with positive connotation), with light. 