I really don't think Xenoblade is really that high budget. Now, I agree that it wasn't a big success, but the game's lack of budget clearly shows once you begin playing. The environments look amazing... sometimes- but that's pretty much the only part of the game that is really high budget looking. Monster models are often recycled, without even texture variations (most monsters seem to have one or two texture variations but 6-8 actual stat variations with different names). There's no VA at all for sidequests outside of the main story and Affinity Quests.
Even in the main story and Affinity Quests, many "cutscenes" are just the characters talking with preset animations while the player moves the camera around. In fact, the director has mentioned that budget was one of the reasons the game doesn't focus as much on a cinematic story, since that's usually the most expensive part of development for jrpgs.
The stuff listed seems to apply to most JRPGs imo. Even the higher budget ones. Pallete swaps for monsters, different tiers of cutscenes, etc.
Personally, there's a lot of VA to me. I guess it depends on what we're comparing it to. Compared to other JRPGs, I'd say there's a lot. Maybe not compared to some WRPGs though. Like most jrpgs imo, VA is used for certain NPCs and cutscenes. Also, I'd say Xeno has a ton more battle lines than other jrpgs. Due to the # of characters, and actions you're able to do in a battle. The cutscenes are definitely pretty static outside of some certain ones, but that seems pretty in line for jrpgs.
And the world is huge as you mentioned. I'm not a "dev" (just done rpg maker), but I assume that wouldn't be cheap. I always felt there was a difference in dev costs between a large detailed world.....say in a Mario Kart 8 track, versus in a game where you interact with every inch of that world....like in Xeno X. I mean, just doing collision detection for every piece of land in the game (so you don't fall through the ground or have things bug out) seems like an endeavor. Whereas in a game like Mario Kart again, you wouldn't need to worry about stuff like that. And being able to jump at any time in Xeno, which not every jrpg does obviously, would just add to that dev time and testing. So you don't get a glitchy mess. I could go on, but I don't to type too much
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tl dr
I'm kind of delving a bit, but the point is that I don't fully agree with your reasoning behind Xeno being cheaper than originally thought. Playing it has made me actaully increase my initial "estimation" in my head. I'm not putting it near AAA tier of course though. And the dev did say it wasn't a super high budget, so who knows what that means exactly. And if the budget is decent, I don't think doing 100k in japan is acceptable. I wonder what NPD will bring.