I have adopted a similar method for new construction. SP or unswitched duplex $25 switched duplex $30 3-w $35 4-w $45 GFI $35 paddle fans $120 + fan more for light kit recessed 6", step baffle $100+ phone or catv $35
Old work is normally TM+. Some customers don't like not knowing what their bill will be, but I need to protect my family. If they want a fixed cost I will go high.