On a Sunday evening I might consider charging overtime or double-time, perhaps also an Emergency Response Charge. You might also consider having a Travel/Service Charge, and also a minimum fee. I think the Service Charge alone would have been very helpful for you in this situation. You should also be charging for the time to go to the supplier.
Dave
P.S. $1000 job-10% discount= $900, not $280. There's a big difference between discounting it and giving it away.
