The VIP Tours are priced to a level now that positively disqualifies all but the wealthiest guests. Most days it is $5250 for the minimum of 7 hours of tour service, while Disney pays perhaps $140 in wages for the day for that guide (obviously more with overhead, benefits, etc) but still it's a great ROI for the company.
From a guide perspective, it is a highly coveted job and the gratuity involved absolutely trumps whatever Disney pays. They have literally zero problems staffing for this job I'd imagine.
The real downside for VIP Tour guests is when FP is operational Disney is insistent on the guides using the FP+ queues which can often take 20-30 minutes when preshows are included. Six Flags and Universal, on the other hand, basically gets VIP tours right on the rides. It's their way of trying to make it seem like the tours aren't getting anything too special, while also maximizing profits.