PLEASE do yourself a favour and stop carrying out commercial work without a quote beforehand!!
In commercial work it's highly advisable to provide a written quote and get it SIGNED before you even open the door of your van!! 9 out of 10 this'll be unnecessary but the 10th one will p you around.
I'm in court soon to get 400 quid out of a firm who flatly deny I was ever in their building cleaning the carpets the cheeky f******s!! Just because I "can't provide any evidence that the works have been carried out", in other words I haven't got a bit of paper with a signature on it saying the job was done. Bit difficult if I was in there on my own with a key to lock up, but hey... learn a lesson, get a paper trail in place before it's too late. There's nothing worse than not getting paid
The other problem you get with working without a quote is you may get a customer who thinks they're going to get a bill for 50 quid and you price the job at 500. Some people haven't got a clue what sort of thing to expect, and you may well lose them for repeat work if you give them a nasty shock. Get the cards on the table beforehand, commercial customers are different from domestics.
But aside from that, a sensible price for the work would probably be in the 350-400 range. Mark's "going in low" at 52p a foot isn't low at all and I think he knows that, just trying to be a bit flash :
No offence meant, just the feeling I got from reading the post!
If you were quoting to win the job you'd probably not get it at that price, you'd be under-cut either by a splash n dasher or by someone with a truckmount who'd probably do it for a couple of hundred, in half your time or less.