Pre Buy Inspection,

My wife and I are closing in on the purchase of out first class A after looking at about a dozen.. We currently live fulltime in TT. I know everyone advises to get a inspection before buying which is good advice but I wonder what is they actually do that we can't? Now, I'm speaking about the MH body not the engine/ chassis. We have spoken to a couple of tech's about the inspection process and they are not very clear on what it involves other than seeing if all the systems work. We feel pretty confident that we can turn things on and off, check for leaks, and run the slides in and out. We have owned several RV's in the past and have repaired many small items, roof resealing, wiring updates, etc and are having a hard time justifying a quote of $1000 for this service. We will have several days if necessary to check out the systems and it does have all service records. Am I missing something?