Joy flights are usually priced similarly to the solo rate of the aircraft
Well that pretty much sums up the state of the industry - it was certainly not the way that I operated.
To operate under someone's AOC you will be supervised by their chief pilot - after all it is their balls on the line. If you go down that path make sure there is written contract - otherwise if something happens you could very well find both insurance and CASA to be huge issues. Also make sure you personally check that aircraft used is insured for both hull and carriers liability and names the operator who's AOC you are operating under.