There are many times when we need to finalize a deal on the spot.
There might be a cash flow problem that could be resolved with the deposit from the job or maybe the feeling that if the deal is not closed right then and there, it might slip away for one reason or another.
But in many cases, there are unresolved details that could stand in the way of a quick close. This is where "To Be Decided" can be used. While TDB is, without a doubt, a procrastination, it can provide your prospective client with some time to make choices without stalling out the entire project.
TDB can also be a trap and needs to be used with some discretion. Small details like specific molding profiles, placement of fittings and the like can be decided upon later without having much effect on the overall project cost. But some things can end up being decided in a way that can run the cost of the job up to a point that is beyond the available resources. So it is important to include some kind of cap or range of cost. This is most often in the form of a "not to exceed" amount.
Do not make the mistake of omitting this or you could easily end up in one of those impossible situations in which the client expects something that is totally beyond what you are being paid for the work.