Well the answer is "it depends". Obviously people will buy a GPU from you, as long as it is in good condition (or even in perfect condition, since I assume you will not use them). But, you must of course sell them less than the price you can find in stores or online.

The price of hardware will go up if the supply is not enough. The whole China-Taiwan situation has caused a decrease in supply. Please inform yourself through valid websites, since I have the general idea, but I don't want to misguide you.

Regarding Bitcoin
Since you posted in the Bitcoin mining section,  it is true that GPUs are not profitable anymore. In order to make money you have to generate coins using ASIC miners which are specifically designed for this purpose. Therefore, I believe you will not be able to sell them to people who want to mine. Take a look into other coins / chains though, because there may be some other coins, where the difficulty may be much less than Bitcoin's and therefore, GPUs could be profitable. Perhaps I am wrong, but I would look into it.