One of our GC's specializes in Restorations. When I write up a bid form him, he has me to include a fixture allowance based upon my opinion as to replacement cost back to original. He then tells the customer that they can go to the big box stores and spend the whole wad on one or all the fixtures, but any overages is theirs. Sometimes the customer just says, if the EC (me) can buy all my fixtures for that amount, then let him. (Of course, I gave them a retail price.) Only once has anyone complained that my fixture allowance was to low.