For fuck sake dude, if grandma is still polishing knobs for a living at 65, give her a fucking brake, and pay her a fair price. She probably has prescriptions to pay for, and physical therapy..........
Wow! Clara Peller was some GILF back in the 1980s. She was born in 1902 and if she were still alive she'd probably charge as low as 12-15 bucks to do the sex. At that rate I'd show her the beef and tell her not to forget about the figs underneath.
These are all valid points.
I am hard pressed to answer, either way.
I think perhaps you should pay full price once.
Depending on how the service is, perhaps ask for a discount the NEXT time.. or give a tip the prior time.. depending on the outcum.