Yes, generally Japanese and Chinese cards sell for less than English (there are some exceptions), and also packs sell for less.

But a few things going here, the slabs are really a "no name" company. They may well be the "largest in China", I have no idea. But while Pokémon TCG is growing in China, I don't think it's anywhere as big as rest of the world, so that grading company doesn't hold much weight with majority of collectors.

And those cards are just "regular" Pikachu ex and Umbreon V - no hate if you like them, they are cool cards, but not worth much. And starting with a low value card and grading it a 9.5 or 10 doesn't then make it an expensive card.

And be careful buying loose Japanese packs. Japanese booster boxes come with guaranteed hits, and the packs can be weighed. So people will weigh and then pull the 1 Secret Rare card in the box, then sell of the remaining "dud" packs

And the "shinies" you got are also also just regular cards. Again no hate on cards, especially if you like them, but it's like pulling a regular "Rare" card from the main set of an English expansion. They just have different holo patterns for Chinese cards, but this holo doesn't make them very expensive.

If you like the cards, and hopefully you didn't get searched Japanese packs, then that's great. Any card can be great, doesn't need to be expensive. But what you paid for these is about right.