Dear Thorium;
If I assume that in most cases with “Vacuum” you are meaning “Pump” instead, then you are half (maybe more!) wrong! ─ and half right!
Because > 4000$ are a lot of ….:
Please! ─ Re-read/study my both last posts (#13 & #15) at least once again, with much more care!!
I DON’T sale Pumps!, ─ And I don’t like to be responsible for your decision under such conditions!!
Not advice!, I gave you hints (including Reasons!), maybe worth to think about!
It is impossible to give Advice if I know NOT anything about application, environment, and staff.
About CFM: Many Thanks to Mr. Dr. Eugene Dakin (Eugenedakin) for the following Link:
"Vacuum Pump Sizing (CFM) (http://www.liquidcontrol.com/etoolbox/vacuum.html)”
But take very much care that the graph therein is only an Example, and differs quite a lot from Pump to Pump (mostly not only by Type) and from Manufacturer to Manufacturer!!
Sorry! that your last post is telling such worse!
Good Luck!
ARGOS++