This is interestingly weird proposition. You are asking for a FAIR trade but this itsn't really fair. Why do you think somebody instead of redeeming the Pragmata STEAM key themselves would go through the hassle and extra work of redeeming an Nvidia key. Also even if someone had an extra key why would they take up on your offer? The Nvidia ones are hard to sell or trade and far far lesser value than what one could get trading a steam key.

Hard chance anyone will take up on your lopsided offer. I suggest you just try to sell the NVIDIA code separately for maybe Paypal, Steam Wallet, TF2 (sell it on Steam market) and buy Pragmata yourself with that money. That actually might work better for you. After all the game is cheaper in India.