I won a coin in tonight's auction. I posted it in "Newest Acquisition" thread. I didn't watch too much of the entire auction as it can lead to un-researched purchases, but anyway, while waiting for my coin to come up for the live auction, I watched a number of coins. I saw many being sold for well below FMV. My experience with Heritage is that you will pay FMV or a premium for "A" coins.
I guess I was watching the A coins then. One that I really wanted (1931 S Lincoln PCGS MS65RD) went for $700 after BP! Another one graded the same with a fingerprint on both sides sold for about $40 less. I was blown away by these prices.
I think you are right - well especially with a live audience. If I sell through heritage again I want everything on a platinum night. That is not a guarantee of more money, but I think the potential is there. I do know one thing - I saw a small motto two cent MS65 brown go for what I typically think of for ms64 prices. I think it closed at 2350 - only paid a little less for my 64 brown.