When you restock from NPC shops, is there a point where you stop buying certain items? For example, if an item is selling for 80,000 in player shops, and an NPC has 3, I will buy them all, or as many as I can. But if there are 5 or more, I leave them. But should I still buy?

I hope that makes sense, lol

It depends on a lot of things. For me the 5 second wait drives me nuts and I often won't buy more than a couple of items just because of the wait. I get impatient and would rather have a bunch of different things than a pile of a single item.

If you're buying for selling purposes, there are a lot of people who don't like buying from shops that stock "too many" of an item. I've noticed, for example, that if I have 3 of an item in stock, they sell normally, but if I have 10 they sit there forever unless I really underprice (unless its currency type items). Of course, even if you have a huge stack you can choose to only put a few in shop and stick the rest in the vault. Still that's extra work.

Some people do like huge stacks though and their shops seem to sell stuff just fine. So, whatever works for you.