[jcrawfordor]

Typically in an auction, a situation where you are bidding price-per-item for multiple items would be described as "24 times the money" or "24 x money". Only some auctioneers do this because it is confusing to novice bidders. Seems to be more common in live auctions than online.

"24 ea" would generally mean that you're bidding one price for all 24.

Your price may be increased by a buyer's premium as well, but again, this is more common in live auctions than online auctions. Typically it would be in the paperwork you sign to register for the auction (...which online auctionhouses often don't do at all).