I don't think its true that if you pay more you get a better instructor, for a number of reasons.
I have flown at cheap schools who have had brilliant instructors and at very expensive schools who have had not very good instructors. The school's reputation sometimes attracts a certain calibre of instructor, and if the school is any good they won't employ instructors who aren't good at the job. Nothing to do with money. Sometimes it is better for an instructor to be paid a little less but work for a better (albeit cheaper) school.
And also, the amount a school charges doesn't necessarily have any relation to what they pay their instructors.