you think its free. its also mines like mainnet btc and requires CPU and GPUS .
You are right and wrong in the same time.
Yes, the mining effort means money and some may feel they could recover some costs like this.
On the other hand sales of tBTC may cause the testnet get reset (see [1]).
Some people do have plenty of tBTC and send it for free (also see [1]). Some people used to lend/ask for a deposit in an escrow in order to make sure they get the tBTC back after somebody did the tests (see [2]). And some people do buy tBTC (also see [1]).
All this being said, you may have hard times find a proper escrow, exactly because of the "tBTC is for free" paradigm.
[1]
https://bitcointalk.org/index.php?topic=5260892[2] I didn't find anymore the exact topic about the lending, just some other discussion about tBTC you may want to also read:
https://bitcointalk.org/index.php?topic=5260994PS. I won't tell you do in a way or another. I just try to show a bigger picture of the situation.