I was contracted by a client to carry out a number of building repairs. Throughout the work he kept asking for more work to be done. At no stage either before or during the work was any attempt made to negotiate a price. After I had completed the work I sent an invoice. My client thinks it is simply too much. What is the din please and where is the source?
In general, one should be careful not to get into such situations, and ensure that the price for the work is clearly stated before any work is carried out.
Post factum, a client has to pay for labor according to the custom of the place. For building contractors, there is often no clear custom, because each contractor takes a different price. However, depending on the quality of the work, there can be a certain bracket into which your work would fit, and the client would be obligated to pay the lowest sum within that bracket. If your client knew that your rates are higher than average, he would have to pay the higher rates.
Sources: Shluchan Aruch, Choshen Mishpat, 3331:2; Ketzos Hachoshen 339:6; Pischei Choshen, Sechirus, chap. 8, note 11.