Yamaha RX-750

I find that this particular receiver is very rare, hard to find topics and reveiws for this on-line. I understand it's old 1991 I believe, but the few listed on eBay are asking a lot of money for such an old box, does anyone have an answer as to why that is?

Well, the reason can be many. My first though is that this is a very classical product, a preamplifier, a power amplifier, and an AM/FM tuner in a single cabinet. This is all analogue technology, and the analogue part of the world has not moved very much. Thus, the tech is still current.

The design of the receiver is also pretty current - it can work in a modern setup.

If properly renovated such a unit can practically be as good as new - but of course the time spent in the renovation process has a cost.

So, depending on the reputation that this unit had/has it may well be worth a premium price for at well kept and/or renovated unit in good cosmetic condition.