I am a die hard PCE/TG16 fan too! yes your right, the PCE can be had for about 40-50$ at used shops in Tokyo. the first model, white PCE wont work on tvs anymore without a modify, but the black core grafx and duos have av outs.
why they are expensive? I dont know, they were always expensive to start, and while it did sell pretty ok in japan, i guess they are still in high demand, except for baseball games that is. the old saying goes, if you really want it, youll pay for it!