As a tea drinker, a very difficult thing to get asked to do is “just buy me something good” and then get handed some money. The motivation is basically the problem – friend (or family, or whatever) is going to China/India/Japan/Taiwan, and so, the asker thinks, why not get them to buy me some tea? Tea is everywhere in those places, what could go wrong?
The touring friend may have no interest or expertise in tea. If they are not frequent visitors to these places, then chances are they are mostly going to be in the big cities, visiting the nice sites and interesting spots. Buying tea is fun – but on their own terms. If the friend is buying tea, and is not a tea drinker, the most likely place that’s going to happen is a tourist-trap shop or the big chains like TenRen. There’s nothing particularly wrong with those places, but is probably not what the asker had in mind.
Also, for someone with no real interest or knowledge in tea, buying tea is not an easy thing, especially in East Asia. There are a zillion choices and prices are opaque. The difficulty is that the shop owners will steer the friend to what they perceive to be tourist friendly teas. There’s nothing wrong with that, but it probably isn’t what the asker had in mind.
Also, these days, there are plenty of stores that sell online from those places, and the prices are not likely to be much higher. In Hong Kong or Japan, in the proper places anyway, the prices are not going to change depend on whether or not you’re a tourist – what you see is what you’re going to get. In China, and less so Taiwan, however, prices may or may not be what you’re supposed to get – I’ve heard prices quoted that are multiples of what I paid. It’s not a friendly thing to do, but it’s what they do. The friend may actually be buying overpriced tea that you can get online for much less. Going into a teahouse can also be quite stressful. Some places have high pressure sales tactic, especially if they are in a tourist area. It’s only really fun is the owners happen to be pleasant and the friend enjoys tea. That isn’t always going to be the case.
If the asker gives a list of things to let the friend get an idea of what he wants, that’s great – but that can also be a curse. If the friend is visiting a place that they might not go back to again, every hour spent getting the tea is every hour not spent seeing/hearing/experiencing things. And, the worse thing is, what they get can be wrong. So, they spent half an afternoon at a tea market getting the tea, but turns out it’s not quite right (say, a fall tea instead of spring, or a Fenghuang shuixian instead of a Wuyi shuixian – and we’re lucky if we got that close). Or, if they got a carte blanche, they come back with a bag of nuclear green TGY that is just plain nasty to anyone who’s drank tea for a while, but is really attractive for someone totally new. What then? The friend will feel terrible, the asker feels like s/he was cheated… it’s not a good situation when that happens.
There are actually a lot of choices out there to buy tea from the source. Not all of them are equally good, but there are definitely options. The only thing that is really hard to get overseas are the top end teas, and also some of the really rare things – but those aren’t likely to be found by the friend who is just visiting for a week. The rest, well, that’s what the internet is for.
I’ve been asked before to buy tea for people, and I found it hard to do even though I actually enjoy spending a whole day in a tea market. It’s harder for people who don’t know much about tea, and who are only visiting a certain place for a short period of time. It’s not a good way for them to spend their time, unless they go often and know the place well, so spare them and let them enjoy their vacation.