Most of the the people I ride with are fairly good with wrenching, so we help each other out, take turns with driving etc and generally it balances out. Some of my mates have tools that I don’t, so I go round and borrow stuff, but do the majority of wrenching myself.
If I was riding with someone new and they had no clue about fixing bikes, then I am happy to help teach them for free and let them use my tools etc.
The key word here is teach. If someone expected me to fix their bike and couldn’t be bothered to learn, then I wouldn’t charge, I would send them to a LBS.
If your mates are really not interested/don’t have the time and you actually enjoy it then I’d recommend half of what a bike shop charges.