This game doesn't really travel much outside Taiwan or maybe China, so it's really unusual to see in English speaking circles. If you look in the wrong places, you would maybe think it's some kind of holy grail, but in market places like Ruten and maybe Taobao, it's uncommon but not all that unusual to see the NTDEC unlicensed releases.
It's probably more uncommon or a little rare over there rather than common, so it's still going to be worth a little bit even if collectors won't be excited unless it's a CIB copy. Like most of NTDEC's output, it's a pretty simple game and can also be found on their Asder 20 in 1 cartridge.
Low supply, low demand items are always a little arbitrary to price with the lack of a market, but I'd probably place fair market value for this at about the $50 mark. (Personally, I'd think anything over $100 would be REALLY pushing it, but I also can't say I've personally dealt with this one.) There's a game on Ebay from the same manufacturer and time period that's been sitting on Ebay for a few months for that amount. https://www.ebay.com/itm/17546061009...MAAOSwCEdjVNH0
Still an awesome find for a cute game that's pretty tough to track down in most places in the world. I hope you've enjoyed having it!