I cannot answer your question specifically as I have no idea what other local FTO's charge out for a R22, however, during the era you commenced training
crude oil was hovering around the $100.00 a barrel.
At every single slight $1.00 increase, we saw FTO's immediately jumping upon the bandwagon increasing Avgas even on old stocks.
Fast forward 2 years with crude at it's knees at around $30.00 a barrel [and falling ] and we do not see much in comparison of the savings. Interesting to see what happens when crude plummets to $16.00 - $22.00 a barrel shortly.