Buying a display ? Dedicated PC ? Of course not, nothing of that. I think (almost) everyone today has a PC and no need to have a dedicated one and no need to have a display if you have your PC -> display cost equals 0. For example I have bought an USB logic analyzer for a fraction of the price of a standalone logic analyzer (Intronix) and I don't need a dedicated PC (which you would argue bring the price to the same level as the standalone L.A.)
Anyway I started the thread to discuss technical ideas how to build such an device and not if or why yes or no.
And even if you would be correct with the price, we do things for fun,
this is our hobby and not a business.
Petr