C'mon mixture, it all comes down to hardware reliability - the software is the same.
(a) Hardware reliability is 2/3 of the problem
(b) The software is not quite the same, its not like you can run any nix/nux of your choosing... you have to run very specific operating systems that have been heavily cut-down to fit the limitations of the product.
I'm sorry. I've seen too many penny pinching clients in my time. Most get denied their request, but for special customers I've occasionally complied with their request because I know I've had solid T&Cs in place and the solution wasn't for production use. The penny pinching always ends up blowing up in their face once the full lifecycle kicks in.
Using the Raspberry Pi in this scenario doesn't even comply with the old "pick two" motto .... its more like "pick one".... the one being price at the expense of quality and reliability (or whatever other two factors you wish to name).
Extra decimal point ? More like dropping from somewhere in the late 90s to somewhere in the early 80s !