Those who charge for inspections, do you have a flat rate or does it depend on the porperty?

I think you were right to increase the price. The inspection isn’t just about the square footage, it’s about the time, complexity, and level of detail required to properly assess the property. A 10,000 sq. ft. home with six levels and all those additional areas could easily take several times longer than a standard inspection. If you’re pricing based on the work required rather than simply having one flat fee, you’re protecting your time and making sure you can actually do the job thoroughly.