If I am planing an extended stay that will require laundry I check the hotel amenities for the location to make sure they have laundry room, if I am unsure I will call the facility first and ask what they offer and get an idea on prices so I have the correct coins/currency.
I was staying in Bangkok once and the hotel charged $3/shirt ... (there were plenty of places to go for less I didn't pay that) but I took a wrong turn one day and wound up in the parking garage and found the laundry service the hotel used ... if you dropped off the shirt yourself it was $1/shirt ... (still more then the .45 across the street)