Cap'n ... I am PRETTY SURE you are not in this for the money, but you shouldn't be underselling yourself either ...
I would stick to my price, and if I lost the gig, I lost it ...

As for your 'following', which I am sure you have, I wouldn't bet too much money that they are going to stop going to this restaurant just because you are not there ... UNLESS you land a gig in an equally good restaurant... Unfortunately restaurant goers are there PRIMARILY for the food ... good music adds to the ambience, but the vast majority are there because the food is good ... BAD music MAY keep people away, good music MAY help them stay, but music is NOT the reason people choose a restaurant ...

t.