Here is my logic in general terms:
The digital print life should match the substrate.
A coro sign only need intermediate vinyl, no lam (or maybe intermediate lam if I feel like abrasion might be an issue)
An aluminum sign could last for years, and therefore gets the benefit of cast vinyl, cast lam, and probably a better print quality too.
Maybe it's not quite double the price, but it's up there.
For me...... your thinking is quite correct, but it's about 15 years behind the times.
These are digitally being printed... with or without the lam is not the question.
Let's try it this way.......
You make a sign and it costs you $XX amount of dollars to make said sign.
You now make it using all the same ingredients except one and your cost went up $4.00 in doing so.
I understand increasing for the sake of a better quality, but to completely double it as Addie mentioned is pure nonsense.
He pulls this sh!t out of the air and then spouts it out like he's some real estate genius and he's not in the real estate business or the sign business. He's a secretary for his Mother. He does this stuff on the side as he's already told us.
His theory would be.... you sell a set of magnetic signs for $135. a pair, but if you letter the door directly using the exact same materials, colors and sizes and charging $300. lettered directly on the door. How do you explain to your customer that since you took the magnetics out of the equation, it now costs double for the exact same thing ??
You need a plan and a structure... and you should follow those guidelines. Otherwise, just pulling numbers out of the air.... you'll end up doing your mother's clerical work.