[001sky]

The slower/faster thing is really more an issue about iteration and time to market for projects. Project costs are a function of overhead--in addition to piece-cost. Overhead is a function of speed and thus project cost is a function of speed. This cost is/can be an order of magnitude larger than the unit-piece-cost. In other words, if you relax the speed constraint you implicitly relax the cost constraint, at least in a normal context. But these tradeoffs (and choices) depend on understanding a project's scope/spec. You are high-light at least one edge case, though: the home DIY, where time is no value but unit cost is paramount. In this case 3D printing might be a good idea, provided your project is suited to such an ouput.