Look at his other items for sale. $800. must be his favorite number
He is using the $800 as the "buy it now", but if you read his description, he states,
"I have to many to list one by one so let me know if there is something in particular you are interested in and if I have it then you can submit the offer as the price we agree on".
He's saying to go to the
"Make Offer" box with that offer and if he and buyer basically agrees on the dollar figure, then he will accept. If not, then if your familiar with eBay, then there's offer, counteroffer or decline offer seller/buyer can click on.