You are correct about the title! One of the big attention getters for me was to see how folks were actually planning to build a regulator when first spotting this a few years back! Turns out they were just screwing the parts of a system together.
but then the idea is very good, no matter what we call it. I never buy a ready made set as most do not have good quality in the small parts. I go middle of the road on the reg as it is a pretty simple minded thing and even the cheapest will regulate the pressure. I like the Clippard solenoid for many reasons and like the middle of the road value of Fabco needle valves to combine them with Dwyer flowmeters for a far better way to monitor the flow.
Many will think of splitting the flow as something to use a manifold but when looking at a manifold, they can be as simple as adding a tee into the existing line. Anything that adds more outlets may be considered a manifold, so design it for what you want, not what is ready on the shelf.
I have used regs in several different ways at work and I do not recommend a used reg that is living outside! They get abused dailly and that makes those used by folks like lab workers, nurses, etc. a much safer bet. Go for the pretty shiny ones that are not beat up every day! They don't get frozen, flooded, or left in the heat to fry that little rubbery diaphragm inside!
While we can actually trim some expense by doing the study and careful shopping, it is really hard to beat the price and ease of buying the small parts from this :
Looking at the costs involved, I find it falls this way:
Excellent solenoid if combined with a salvage 12v power supply that you might have in a scrap box? We might buy it off the auction site for $15 but that is after we spend a good amount of time to sort out the model numbering and if we choose the correct one from dozens of options.
Set on a manifold that sells for around $25 and I only find through distributors.
Good middle of the road needle valve and we might buy it for $40 or so.
Small brass parts might be found cheaper but takes a bit of study as well as running here and there to find and fit the correct ones.
So once we add in numerous shipping charges due to none of them found at the same place, distributor markup, etc. we can really lose a lot of time and value to save a bit. Money can be valuable but sanity has a price as well?
Simple to do the work if one has a bit of mechanical in them but the decisions and shopping can kill you!