I expect that saying this might upset some people, but in my experience it's mainly Japanese and Western people who really care a lot about there being precisely 181/180 stones in a set.
It's quite rare for a game to go for more than 300 moves, so being able to cover the whole board with stones is sort of overkill, especially if you play with Chinese rules.
A lot of cheaper sets from China and Korea don't even have 180 stones, but 160 instead. For example this one:
http://shop.gogameguru.com/go-bento-box/ and various glass and plastic sets that I've had in the past.
I've found that most Chinese and Korean people really don't care how many stones there are in a set as long as there are 'enough'. They're more interested in just playing Go and the stones are a means to an end. The exception to this is when buying an expensive set of slate and shell stones (or stones some other expensive material like agate), because in that case you're paying for quality and that usually involves the service of having 181/180 stones carefully counted out.
I've had the experience of asking both Korean and Chinese manufacturers about whether there were 180 stones for cheaper sets and was treated like an idiot both times. (note that Yunzi are Chinese stones)
Normally if someone tells me they've received a new set with some stones broken on arrival I'll send them new ones as a service, but in Hebsacker Verlag's defense they seem to have fairly cheap packs of replacement stones on their site (I've just been looking at it), which is a good idea for later.
I used to sell Yunzi (before starting Go Game Guru) and they do seem to be more brittle than other glass stones, and hence break more easily during shipping. It's also quite possible that single convex stones break more easily because the shape isn't as strong.
EDIT: Oh, Hebsacker Verlag replied with a link to those stones while I was writing this
)
