Yea, I've been trying to figure out where they came up with that price.
If I had to guess based on their description, there is 35k parts there. That would be $10 for each part.
If you think about it, that means you would have to average $20 each to resale. That's based on overhead for storage etc. and some profit. So... of those 35k items, some are going to be less than a dollar and some are going to have to be over $100.
Since he's been selling for a while, you can bet the 60's muscle car stuff that brings in high $$ is already gone. Now you area left with earlier and later stuff. The ad states to 1999. That means a lot of K car and other FWD junk is going to be intermixed. There's also a lot of aftermarket parts that never command a high price, especially if those parts are still available. Then there's stuff like master cylinders, hoses, calipers etc. They have a limited shelf life. That means you can expect to have to rebuild a NOS master cylinder that has been sitting on the shelf since 1954. Buyers know that and won't pay much.
IMHO, he's just testing the waters with an outrageous price. If someone is serious, they will look at what he has and make an offer. If not, then his price keeps the tire kickers and wannabee parts dealers away. Who knows? Someone may even pay that much! If nothing else, he's generated some interest in his parts.