I charge by the fixture, it works for me. I get 275 to 350 per fixture. I find it takes less time for the bidding process and it also gives the client the tools to figure out what the costs are. It especially works when I am doing jobs in phases. There are some jobs that use more or less wire, etc. but it seems to even out well. I also don't have as big a fluxuation in property sizes that some have outside of CA. I do bid a lttle differently on the 200-300 fixture jobs. My competitors charge 185-225 per fixture, but they still think it is all about the fixtures. For me it is all about the results.