Not sure if this covers your question, as the OP said "the same computer with Windows and Linux available" but at least you can probably find the equivalent Linux machines here and then compare to the previously found Windows systems.
Just do a websearch for "Dell Workstation". Look at the Precision 3630. Some say "Precision 3630 Tower Workstation" and some say "Precision 3630 Tower". Scroll down and you'll see that where it lists the operating system, the systems that say "Workstation" all have a "show all options" listing.
Customize the one that is currently listed at $579. It has an i3-9100 processor and switching from Windows 10 Pro to Ubuntu will subtract $109.27. But if you then switch the processor to the Xeon E-2246G, then changing from Windows 10 Pro for Workstations to Ubuntu is a price reduction of $264.36!
As an aside, I find it hilarious (and nice) that you can save a couple dollars by specifying no keyboard or mouse. Sometimes, you'll even see the option to have them skip shipping you a power cord for $2 off or something.
