Internal fraud was incredible. One day just about the entire warehouse staff and I want to say a third of the floor staff was fired. If memory serves, the warehouse manager discovered that a large number of specialty "Made for Compaq/Dell" RAM by one of the major RAM vendors had its "COST" value set very wrong (to like $5.00 or something like that). The price paid by employees was whatever IMS said "COST" was. So a $350 memory chip could be purchased for $5.00 by an employee. After figuring it out, of course, he shared the knowledge with other members of staff who participated, as well. Dad always said "if it seems too good to be true, it is", so that -- alone -- was enough to keep me from making that mistake.
The other scam I recall them running was taking items home that were supposed to be destroyed per agreement with the manufacturer. It was very strange coming to work one day and finding out about half of the staff I used to work with was let go for fraud...
[0] We had this one local gentleman who was notoriously frustrating to handle. He'd come in with a million questions, spoke very poor English very quickly and became frustrated to the point of yelling, I think, "F** YOU" at me/storming off when I told him I was having a difficult time understanding ... due to an ear ache (didn't even mention said English; I was pretty good at understanding thick accents, normally).
[1] Not as great as it sounds -- I doubt it was "invoice cost", but if it was a PC/laptop/anything terribly expensive, it was frequently higher than the price of the item.
Corporate customers were usually paying on pricing terms that were "X% above cost". And enterprise sales had flexibility further to close a deal. These one-off products had something to do with that -- perhaps it allowed them to offer pre-configured systems for some customers that calculated to the agreed-upon price when their % above cost was calculated, or maybe it was just a way to "throw in the RAM on all of these shiny new Packard (Bells)".
CompUSAs big shrink issues were more organized criminals popping boxes open or flooding the store. I worked at one that was hit by a crime bus — 50 mostly non-English speaking Asians would occupy every employee and loot the place. (They hit all of the big box retailers in our area). The biggest issue was internal fraud.