Sorry for not introducing myself before posting here, but I found this thread after seeing the youtube video and thought I'd chime in with my thoughts.
The simple solution to the problem is, if you can't justify the price, don't buy it. We're not talking cancer medication or some necessity, we're talking about a modded n64 for crying out loud.
I also realize people are also entitled to their opinions, but I'm seeing the same people posting over and over about how this is ridiculous, I think once is enough to voice your opinion, if it hasn't driven down the price, repeating yourself probably won't help.
I respect the creators right to charge whatever cost he wants and I think everyone here should as well. You can't force him to do anything and neither should you be able to. If he wants to sell it bad enough he'll lower the price until someone bites, but I have a feeling he wants to keep it for a bit considering the 700+ price tag.
What I would like to see though is some sort of tutorial or documentation on how SlipStreamGT pulled this mod off. It doesn't seem that complicated but then again I haven't done it.