An 100hr inspection costs $1200? Is that an error or are they really that much?
Henning's post above does not apply to this scenario. Yes, that's about what I figure it will cost, it's no less work than an annual. When you figure that the oil is also going to get changed, the tires will probably get changed, the brakes need attention about every 200 hours, and there is bound to be something that has broke in the last hundred hours. I really try and only do maintenance during 100 hour window. This means deferring things that pop up between 100 hours if it can safely be deferred. So there is more to it then just the inspection itself.
In addition we're going to burn about $100 in avgas getting it to the airport where we do maintenance and getting us back in another airplane.
Sometimes it is less, sometimes it is more, for budgeting purposes I use $1200.
Now rental aside, some of those costs we'd still have if not renting, but we wouldn't be changing tires every hundred hours, or going through brakes so much.
Things you would do as a private owner, like owner assist, to keep costs down aren't really practical in a commercial operation. We're trying to keep up with usually 6 to 8 airplanes. If I owner assisted all the maintenance I wouldn't have time left to actually make a living. It's hard enough just to keep up with instruction, following up on leads, billing, maintenance tracking, ferrying airplanes around, retrieving ones that people get stuck places, dealing with the TSA, FAA, FBO, airport authority, and whichever other government entity will want to get involved next month.