Costs of some things:

A double hotel room, not fancy but clean, usually with bathroom, in a not-dumb location: $20 (small towns) to $40 (big cities)
Hostel bed: $4-15 (the low end can be pretty dank (as in socks, not as in memes))

Meal of noodles, baozi, dumplings, or something else at a little joint on the street: $1-2
Meal at a sit down restaurant with a menu: $4-8
Hot pot or other fancy meal for two: $20-30
Watery Chinese beer: $1.50-2.50. But at a bar it’s not just “buy yourself a beer”; you buy like 6 or 12 for table then drink shots of it. You may drink a lot of beer quickly, but it’s probably OK because a lot of the beers are 3% ABV.
German or Belgian beer in a fancy bar: $5-8, and then you sit there with one beer for yourself you selfish antisocial goober
Tea: you usually can’t even buy this, it comes with the meals and is green and weak.
Tea at a teahouse: $2-3. Yesterday I tried to buy tea with fruit and sugar at an outside teahouse and she said “yi bei, er shi”, which means “one cup, ¥20 (about $3).” But I thought she said “yi bai er shi” which means “¥120 (about $20).” So I made a face and said how that’s too expensive and got a beer instead. I’m wondering what she thought of the whole thing.
Coffee: $4-7 (or $33 at that bizarro-world drug front coffee shop we ran into) By the way, the best coffee shops in Western China, based on my extensive survey, are Xiangcheng Coffee in Shangri-la, Greenhouse Coffee in Xining, and Let’s Grind in Chengdu.

Entrance fees: significant! Yading and Kanbula were both $40. Lots of others for things like Yubeng, Zhangye Danxia, the pandas in Chengdu, Songzanglin monastery in Shangri-la, that Qinghai Lake tourist trap, and some frickin' gorge in the middle of nowhere outside Xiahe where some goons set up a ticket booth were in the $10-15 range. I mean, they’ve got you over a little bit of a barrel because it’s clearly worth it, but be sure to budget for these.

All day bus (e.g. Chengdu to Zoige, or Shangri-la to Daocheng): $20
21-hour train, hard sleeper (which is not “hard”, really, it just means that there are 3 bunks, not 2): $45
2 hour express train: $15
Hiring a car and driver for a day: $70-100
Gas: $6/gallon

A nice thermos: $15
A nice scarf: $15
Cheap baijiu (liquor): $1 for a 6-oz bottle with a beer bottle cap
Expensive baijiu (Moutai is the one brand I know): $200 for a big bottle
Cheap Pu-erh tea: $0.15 for a one-serving rock
Expensive Pu-erh tea: remember those old ads for K’nex? “If you can imagine it, you can build it”? Well, if you can imagine it, you can pay it for Pu-erh tea.
Is Pu-erh tea really The Best? I mean, up to you, but sure, in the way that caviar is The Best but so is peanut butter.
Clothes: not way cheaper than the US. You could pay $20 for a shirt or pair of pants that are probably like a step down from Gap. You can get amazing sayings on it though, so point, China.

Some more thoughts about gear:

Phone: we are clearly in the age of the smartphone. (This is not a given. 5 years ago we were not.) So glad I didn’t bring a computer.

Coats: if you’re going to China in July and August, you don’t need two down layers. I still like my current plan of rain jacket shell + down jacket + down vest for when it’s really cold, but God it was 80 degrees for 90% of this trip, I really could have skipped the vest.

Toiletries: I thought I was really clever by packing one toothpaste for the both of us. Guys, don’t do dumb micro-optimizations like this. Just bring two lil' toothpastes.
I brought one 4oz and one 2oz bottle of contact solution (ssh, don’t tell the TSA). That was the perfect amount. Or really, the perfect amount is, get Lasik like Tati and bring no contacts.

Oh my god Towels. Maybe bring a towel? For the first half of the trip we mostly got towels included; the second half, I often didn’t. It should be a law that a guesthouse gives you a towel: look, guys, you launder your sheets, just launder towels too. There’s no way I should have to carry this. But anyway, especially if you’re super-budgeting it, maybe bring one of those REI-ish super-towels.

Socks: I’m finally kinda happy with the Smartwool PhD like quarter-length socks. They still make my feet too hot but not wayyy too hot so that’s nice. It might be just finally going shorter than crew-length. Added bonus: they pack smaller.

Amount of clothes: I’m updating my recommendations to 3 T-shirts and 4 pairs of socks. Socks are so small and sometimes you really need new ones. Shirts, you don’t need new ones as badly. (also, 2 pairs of pants, one button-down shirt, 2-3 underwears, and whatever coats you need. these numbers all include the one you wear on the plane.)

Shoes: Got these Salomon something something light hiking shoes that are waterproof and breathable and blah blah but what I really dig is that they have this drawstring doober instead of laces! I can very easily leave them loose and very easily tighten or loosen them. Never tying anything again. Love it.

Vacuum packing bag: I finally tried one. I think it saved me space? It’s kinda neat? It also takes up a little space itself? The jury’s out.

Kindle: wow, when I have infinite podcasts and infinite Ascension (video game) it turns out I read zero. Welp.

Chinese Phrasebook: didn’t actually need this - Google Translate has it covered, and even when it makes you say something that doesn’t really make sense, it still kinda makes sense.

Medicines you might need: only bring a bunch of medicines if you’ll be real rural. If you get sick in a city, worry not, just go into the pharmacy and describe stuff (Google translatin' like a boss), and they’ll hand you three drugs: one will be western-looking (maybe even a name you recognize), one will look like Skittles and have plants on the box, and the third one’s a wild card, could be Western or plant skittles. Take ‘em all as the pharmacist says (they’ll cost $6 total), and something will work. Not sure which.

Plug adapters: you probably don’t even need these! Every Chinese plug I saw can take the standard American two-pronged plug (in addition to others). If something has a 3-pronged plug, then bring a 3-to-2 adapter, but you’re probably only bringing plugs for your phone so you’ll probably be fine.