>>9503955KBB and Jinbao are KOs of GT and DX9 legends OPs respectively so they are half as cheap.
As for DX9, HS02 and MS1.0 at the $60 range, age is indeed a factor, though it is more to do with how DX9 and HS are both dead zombie brands not producing anything new anymore, and MS intending to replace theirs with the 2.0. Plus, production costs have risen over these few years and they are from the pre-covid era.
What you're also missing about NA and MS2.0 are their higher parts count and materials used, due to both of them having more complicated engineering to better replicate the cartoon looks.
If you have difficulty seeing beyond volume though, just get the Jinbao, it's the best price/volume if you put everything else aside. The word is that they've been forced to stop using the mold so there may be a finite stock left on the market.