I think that styles you buy for either the DGX-230, YPG-235, PSR-E463, or PSR-EW410 should work on the other models, but you might need to use a program like MixMaster to edit the voice selections.
I can't speak about other style shops, but at Yamaha MusicSoft you might need to try selecting for a different yet similar model, because there can be wildly different results for models that should be able to play the same styles.
For example, the PSR-E403 and YPT-400 are the same keyboard; they just have different names for export purposes. The same is true with the DGX-230 and YPG-235. Yet if you search for styles that are available for a specific model, you might get more results for one model than for another, even though they're identical except for their names. Or you might get more results for an older model than for a newer model, even though the newer model has all of the voices that the older model does plus some additional ones, so you'd expect the newer model to have more results than the older model-- all of the same styles as for the older model, plus additional ones that use voices which are on the newer model but not on the older model.
I'm not sure why this is the case. Perhaps when the newer model was introduced, the store didn't copy the database entries (i.e., list of "compatible" styles) from the previous model(s) to the new model? Or perhaps some of the older style files weren't listed for the newer model because they had gotten added to the built-in styles of the newer model and therefore you don't need to buy it as an external style file? (Although, even if that were the case, it might still be nice to buy it as external file so you can tweak it in an external program MixMaster, given that the "entry-level" models don't have a way to export their internal styles the way the higher-end models do.)