My RTX 2080 Ti mines bitcoins on average 2G/s according to Nicehash.
However, I see these cheap ASIC miners on Ebay:
https://www.ebay.com/itm/Brand-New-In-Hand-Bitmain-AntMiner-V9-4TH-Bitcoin-Miner-Shipping-from-USA/264204806618?hash=item3d83d569da:g:knIAAOSwmHdbSkui
capable of mining 4TH/s...