Ones like these who sell in sheer volume can make you wonder.
However, they are uacc approved and even won an award for dealer of the year in 2004. Granted that was a long time ago, but its obvious the uacc wouldnt give out that award lightly and especially not to a company who is distributing fakes. So its pretty much guaranteed that up until that time they were legit. Thus it does help add credibility to them and that they still are.
However, you can tell they are buying stuff in bulk. So I guess for the most part you are paying for their knowledge and expertise at buying stuff that they feel is genuinely real and then reselling. They are a JSA consultant, so they must be very knowledgeable to be giving James Spence a helping hand from time to time.
Also they have a lot of no-name autographs, which typically helps add credibility in my eyes when it comes to sellers having this much to sell and sheer volume. If they had only a-list celebs it would be pretty much a dead give-away.
They also have a buying page on their site, which to me helps understand that they are buying stuff as opposed to fake signing stuff.
Does this mean they have never sold a fake? Probably not ... no one is perfect. However it seems they have a very good track record.
When I buy autographs I LOVE IT when I see them signing the actual item ... but if I cant have that I do a google images search ie. Mel Gibson Autograph .. then I view tons and see what sites they are on etc. Typically you can find one where a person has him signing it in person (a picture) so at least you KNOW that one is authentic and you can match based on that.
Al Pacino and De Niro for example have the ugliest autographs ever ... when its them signing its a scribble "here get the hell out my face" type signature ... when they are nice and neat its a Secretary autograph as you can mail a lot of stars and their secretaries sign the stuff instead.