I think HA's consignment fees are only negotiable if you have REALLY big ticket items (a la London After Midnight, Bride of Frankenstein teaser, etc...).
Otherwise their consignment fee is 20% for sig auction items and 25% for weekly auctions. On top of that they charge the buyer a 19.5% BP. So if you see something in their archive as being sold for $500 including BP, their BP was $82. Of the $418 left, they took another $83 assuming it was a sig auction item. If not they would have taken $105. So their final take in the transaction would be 33% ($165) or 37% ($186). eMovie charges a sliding consignment fee ranging from a lot (>50% for low value items) to somewhere around 20% (from memory) depending on the final value achieved. They do not charge a BP. I can't recall Rich's fees off-hand, but I seem to remember them being fixed at like 25% or something -- Rich by all mean correct me if I'm wrong.
That all said, HA does seem to get some of the highest prices for certain types of items. It's up to you to decide if the potential increase in final value for your particular item would offset the added fees. If you have a bunch of pre-60s stuff, HA may serve you better. If you have lots of high-end 80s material I would think eMovie might be a better venue -- especially as of late.