This is a real auction, not Ebay. There are plenty of terms and conditions, lot fees etc. The estimated retail is what it's worth normally. They are saying $20K, which is probably accurate if you just fixed the damage, repaired any rust, and resprayed. They are estimating $15K in repair.
Hitting the $10K reserve will guarantee you the car. However, you can offer $7K, and be the high bidder. The seller can then decide if they want to let it go for that price. If you hover over the link it kind of explains this, but not well. Also, the site will cover the expense fees also.
I almost bought a salvage E28 with a spectacular interior on co-part last last year. I called the yard and the receptionist explained it all to me. Just remember, it doesn't work like ebay and it will make a bit more sense.
I think it will sell for $7K. We won't know because the bidding process is silent. I still think it's worth that much...