Somebody asked me to look over their cost calculation for an internal IT project in the 1.5 mio € range. They did some eyeballing, and are now asking me to cross-check it for them with a few hours of effort. There is no malice involved, i.e. I am 100% certain that they won't blame me for anything that happens now or later, no matter what my conclusion about their project is.
The project includes software, hardware, and time&material for installing the latter; the hardware and the T&M are special enough that neither I nor anybody else outside of the project know much about it.
Obviously, it makes little sense for me to go number-crunching now, as I know nothing about their project except what they already knew and used for their calculation. I also don't want to simply say "no". So my plan is to teach them a small hands-on method to do the work themselves (maybe with me consulting/moderating).
Do you know of a good way to check such calculations? I know that there are many methods for this kind of work out there, some of them very involved, but I am specifically looking for one which fits on 1-2 slides, can be demonstrated/introduced quickly, and which at least gives some measure of improvement beyond just going by gut-feeling, within a short 1-2 day workshop.
They are not going to base the final go/no-go on this; it is more a "should we go along with this at all" decision right now.