All folks seemed to think 20% was no trouble. One guy suggested 40% was possible on some equipment. Some vendors seemed to choke on that suggestion. 
DJ
Depends on the vendor in question. Just like going to the car dealer and
asking for the dealer's invoice: call up Comstor, Ingram Micro, or Tech
Data and ask how much they buy the gear for. Or ask your vendor how much
they pay those 3 suppliers. Some see roughly 36%-42% on the gear you are
probably referring to, unless you buy 10-20 of the same box at a time,
even to include the already deep discounts from bundle pricing.
-Andre