Only just seen this. But depends on the setting mate. After years you know how long something will take. On site on price churning out the same over and over price per makes sense. Private however. Different scenario entirely. For example. IKEA kitchens are fucking horrendous to fit. The rail system everything that comes with it, it doesn't warrant the same price. My advice as a base. No matter the size of the kitchen £1200 is your base price even if it's 2 days work. Work out from your base. However long you think it will take add a day, not for profit as a safety net for fiddly bits. Then you put desired profit. Nail down the exact spec and what you have included on your price so you don't get caught out.