Its amazing the diference in prices folk give for the same job.
The way i see conny cleans is price fair but dont undersell yourself. The people who own that conny must have spent tens of thousands having it built. If they are then not prepared to pay for its upkeep then more fool them.
They would not spend 30k on a new car and let it fall apart and not spend money on it, so why would something like this be different? when I price a conny I usually try to get that analagy into the conversation to make them think about the value of the building otherwise to them its just "part of the house"
I would charge a full days labour for that job to ensure they got a quality job done. (no I am not going to tell you what "a full days Labour" charge is )
