ebay has it's pros and cons. I do search the bay quite abit for the coins i'd love to have.
The biggest benefit for me is
ebay stores that are coin shops/dealers. If they have a coin listed and it's been there for quite awhile. If I'm in the area of the of the store (on vacation, travelling or whatever) I bring in a cash offer of their listing price (-)
ebay & Paypal fees (roughly 13%). I'm 3/5 on doing this (not all I have visited approve of this practice). It's significant savings (to me) on a piece that's priced above $500 and honestly they are not losing money, it's the same, they just have to end the listing if purchased.
I acquired my 1909-S VDB this way (saved me roughly $550.00) and it was my 1st large purchase coin. I was stoked.
Also, I get to see the coin in hand, which is the only way to purchase IMHO.
If you have to travel to get to the store obviously that increases your cost...but if you're in the area anyway it's just a planned,calculated and hopeful bonus.

I don't think this is bending the rules...but it's basically using
ebay as advertising (for me at least).
Note...I was burnt on
ebay on a couple of purchases years ago...so this works for me with no remorse and hassles.