It's just far to generic of a statement anyway. The major auction houses do the best with big coins period. When it comes to niches different niches have different buyer bases checking different sources and one thing may do better on eBay while another at an auction house. But also buyers get free shipping on eBay and no credit card fees which needs to be taken into account for auction house sales
Yeah I can definitely see that being the case. For what I collect (US coins in the $300-$1,000 range typically) there are thousands of examples all over the place and I haven't noticed anything but similarities in final sales for them. I'm going to a live auction coming up that allegedly everything sells for 30% less than anywhere else which I just find hard to believe and have to see with my own eyes. I'm lining my pockets hoping it's true though.
Yea I generally follow that range and really haven't seen any major differences overall. I've actually seen quite a few from eBay that I casually followed in dealer inventories afterwards. Plus no two coins are the same anyway, a few dollars either way in price is a yawn for data There is probably a reason why, but if not stock up on as much as you can lol.