Sounds good, but curious to know how it would work. Would it be a coin you could actually read, or a tired clump like many cheap ancients are?
You won't know until you order it. But I doubt you'd get cream of the crop. For someone who doesn't have access to buying that type of coin locally (like the 2 or 3 for a buck bin) this might be the thing to see if they like that type of coin. But it just might also be a way to spend your money on something you won't care about in the future. Either way, you would probably get a coin that has a little to no monetary value and little or no chance of improving on that. He covers his cost and makes a bit. He's hoping you like the type of coin to then get more involved. I think it's a neat advertisement.
If it were me I would probably just wait and get a nicer example in the $30-$50, rather than have a large amount of most likely, unreadable, problem coins. But, I agree with Kasia and could see how it would probably be good for a very casual collector who just wants to say he owns a coin from the Middle Ages-Renaissance period.