I look at it this way...
If i INVITE somebody out with me i do not expect and offer nor will i accept one, They are out with me because i thought about it, wanted them along as as such they are my GUEST. The same way some one will come over for dinner at my house and i do not expect a bottle of wine, a desert or any sort of payment, If i invite them to dinner then i want them to come and enjoy a dinner with me. However if its one of those "when are you going to take me out!" mates, and i dont particularly have the urge to take them out then yes, i Would like an offer of bait, food, fuel, case of piss afterwoods- WHATEVER... even at the very least hang around and help clean the boat- if not it will be their 1st and only time out. Then again some mates will bend over backwards to help me out, those guys might even be non fishers, as far as im concerned whats mine is there's and i never think of costs they are more than welcome for a social fish anytime rather than a serious fishing session.
I guess at the end of the day it matter who the person is and all I really want is the correct level of courtesy from a person at that level of friendship.
In any case, $10 is a CHEAP day on the water its the least they could offer if nothing else.
Cheers
Musty