cat sitting cost - ranges?

I am wondering what people pay for cat sitting. Last time a few years ago I had someone come they charged me $20 for one time visit (usually considered 1/2 hour) to do the usual - give food, change water, clean litter box, play with them a bit, make sure they are okay, etc. (I had also heard some people pay $15 per visit but I guess it depends on person, what and who you are comfortable with, # of cats, etc.) Wondering what the going rate is if you need 2x per day (just double that or maybe less since it's 2x with same person?). I believe rate went up based on # of cats also. (I know it works this way for dogs.) If the person has to give medication, would that be an extra fee? Thanks for your advice.