Yeah, most liquidation auctions like EquipNet that I've encountered have 15-25% buyer's premiums. Definitely important to factor that into your bidding. EquipNet is interesting in that they have a handling fee in addition, which I've seen get rather high in some cases. Some places also charge fees depending on your payment method. All things to be aware of.
With regard to meter choices, the HPAK 34401A have been going up in price over the past few years. Lots of HPAK gear tends to demand premium prices on eBay.
If budget is really tight, the HP 3456A can be had for $100-200, but be aware of the reduced feature set as compared to more modern devices. Nevertheless, like the 3457A, it's a good piece of kit (and easier to read than non-backlit LCD).
Keithley stuff tends to demand a premium on eBay, too, but you can get those Keithley 196 DMMs at pretty good prices with patience. If 5.5 digits is OK, you can also consider the 199, which supports a scanner card, too.
If you get a good deal on the Keithley 2000 or its similar-looking relatives, be sure to look up the threads here on replacing the electrolytic capacitors as they're notorious for leaking.