In Japan, every hotel or hostel has laundry, and you can do a full load for Y400 or less. There's also coin-op laundromats with similar prices. It isn't free, but it isn't expensive by any means, it's probably cheaper than using a coin locker to lock your suitcase so you don't have to lug it around all day until the hotel lets you check in.
In Europe, many smaller hotels have laundry on-site you can ask to use, or again you can use coin-op laundromats which aren't that expensive.
What countries did you visit that were "cost prohibitive" for doing laundry?
China was a no-go, the major hotel I stayed at in Suzhou was incredibly nice, had a great price on the room, and an expensive per-piece laundry service. The tiny hotel I stayed at in Beijing didn't have laundry facilities for guests.
Shinjuku Prince in Tokyo also had the usual high per-piece laundry rates. I don't 100% recall but I think the Ryokan I stayed at was similar.
I AirBnB'd through the UK, so I didn't have to worry about it. Same thing in Mexico, didn't bother with hotels.
It sounds like you're staying at expensive hotels.
I just spent 2 weeks in Japan. The locally-owned hotels had laundry on-site usually. This isn't full-service laundry; this is a coin-op machine on the ground floor that you use yourself. The one I used at a very new hotel in Osaka (Sarasa in Dotenbori) was really nice; you just put your Y400 in and come back in an hour or so, as it does both washing and drying. At hostels, it varies, but one I stayed at just charged me Y100 to wash a load, but they didn't have a dryer so I had to walk down the street and pay Y200 to dry it.
Did you even look at laundromats? If you're expecting hotel staff to do your laundry for you, then you're not going to get that cheap in almost any country, certainly not any industrialized one.
Ryokan are known to be expensive. Business hotels are much, much cheaper. And yes, AirBnB is a good option too. When I was searching for hotels on booking.com and travelocity.com, I was able to see which ones had laundry there too.
In Europe, many smaller hotels have laundry on-site you can ask to use, or again you can use coin-op laundromats which aren't that expensive.
What countries did you visit that were "cost prohibitive" for doing laundry?