aren't many dedicated miners in India
There are LOADS, don't worry.
If let's say mining/crypto exchanges get banned in India (very unlikely) literally thousands of used cards will hit the market.
Just like in 2018 crash, if that happens, you will see a lot of cards in used market. Some of them would be near the end of their life or past that (GTX 10X0 series and AMD RX 4XX, 5XX, Vega series) and lesser amounts of RTX 20 and GTX 16 series near end of their warranties.
Some of the 30 series cards highly used for mining would be out too.
Considering there are 3-4 generations of cards being used for mining currently, I believe if and when crypto mining goes down, used market will see a large amounts of cards for very cheap.
For example, I bought a Strix 1080TI (the miner had just RMA'd it so it still had its plastic peels and stuff) for 21K in Feb 2021 and that was just before we saw huge BTC and ETH bullrun where everyone jumped into mining.
So after the next crash, it will get even better than that. 1080TI for 22K, 1070 for 12K, 1660 Super for 12K, RTX 2060 for 18-20K, should be possible.
But all of this after the crypto does crash. Which seems unlikely for now. In 2018 the case was different, there was a HUGE crypto crash in India because RBI Basically banned every bank from transacting with any of the crypto exchanges (mostly Zebpay etc at that time). This is not going to happen this time.
Price won't decrease though since other countries will continue to have shortage
I don't think so. We saw a lot of 1080Tis for 25K and 1070s for 13K which is a lot lower than any other countries for their all time low prices as well. Indians generally don't sell to other country buyers, so for used market it is localized.