I’ve always found it the other way round, the ones that have more to lose tend not too argue ( still won’t make you a brew) and pay but the ones that play on the same field as me try their luck and want money off, if they don’t ask and the job has gone well I might give a bit back, if you ask then you pay the invoice, I’m doing a bit for a multimillionaire now and he’s a bit of an odd character but if I give him an invoice he pays it while I’m there and his missus brings me cake