Why can't I just buy it off AliExpress for $6000 + $50 shipping?
You can also find some deals on branded equipment on gov auction sites. People are buying lots there, refurbishing when required and reselling for similar markups.
All of the options require a bit of legwork and elbow grease.
Basically, you're paying more but they're taking all of the hassle and worry and a large part of the risk out of the operation for their cut and you're not paying much more than you otherwise would for the service.