Specification grade

We recently completed a residential project as the design-build entity; we designed and the built the project. Because of cost constraints, I found myself choosing alternative products a couple times. Each product alternative had its own rationale, and I found myself wondering about the specification process architects go through, whether we are serving our clients by specifying top-quality all the time.
One product was a roof drain. I originally specified Zurn Z-125 brass roof drains. These run $200 each. We ran into a procurement snag which could have negatively affected schedule, and the plumbing supply house suggested a PVC subsitute. These cost $48 each. Well, the PVC drains work. I am quite happy with them, and realize now they should have been my first choice.
A second product was for decking boards. I originally wanted to use Meranti, which is sold as a Phillipine mahogany. I've used it before, and it's really nice. However, the price has gone up quite a bit in the last few years, and so I asked the local building supply store to provide pricing for about six different options. We ended up choosing Western Red Cedar, which I love, and which happens to be about the least expensive (in STK grade- select tight knots) decking out there. Plastic lumber turns out to be more expensive than ipe, which surprised me.
I third product was for structural silicone sealant. We did a lot of research on this, and specified Dow 795, which runs about $7 per tube. Well, we didn't need anything that expensive, and ended up using a locally stocked Dow silicone sealant. I'll use the 795 on a subsequent project where we truly need a structural silicone, but it was silly of me to specify the 795 for this project.
Could the PVC drains, the Western Red Cedar and the silicone withstand comparison using life cycle costing? I think so. What is more intriguing is that my thought process changed when I stopped wearing my architect hat and put on my contractor's hat. It would be helpful if I did that at the start of construction documents, when I'm detailing and specifying. Perhaps that is what CDs are: when you stop being the cape-wearing architect and put on your toolbelt, thinking, how am I going to build this thing, on time and on budget?