$200 for 1080ti is a really good deal in 2021, it's already in the too good to be true territory. The power consumption will be higher but it still can get you 40 ish MH/s each card (that's about $4/day right now). What you want to know is why he want to sell them at those kind of price and it's even better if you can test them first to see if they are working or if there's some card that need to be repasted / need to change the fan.