Different toy, different market. This is made for the hardcore fans that really like Zyuranger in Japan and are going to pay a big price tag for it.

Because 1988 pricing and currency values are totally the same as those in 2016.

It's a super limited edition highly detailed vinyl. Articulation isn't the point, so if that's your complaint it's invalid. If pricing is your point simply look at the numerous other vinyls of this nature that X-Plus has produced in the last decade. That are actually more expensive than this Daizyujin. This isn't bizarre pricing and the features of this figure are pretty standard.

i want, but the price, that's a bit of a problem

if i wanted another unarticulated megazord.. i'd just get the original or the legacy version.

it's so frustrating that there aren't "masterpiece" versions of these zords.

Stability can prove to be a problem, though.
If it's an articulated Megazord you're pining for, SRC does have a decently poseable Daizyujin available, but it doesn't convert or separate.