From “Ask Kit!”:
Q: What is the average cost to wash the linens from a guest room?
A: It will cost you about $7-8 per double occupancy to do sheets and towels. That cost includes some pay for your time, as well as water/fuel/soap costs. Note: this cost will fluctuate with the size and quality of sheets and towels, your location and utility charges, and of course inflation will have that expense rise through time; when I was an innkeeper in 1988, my costs were closer to $4/double occupancy.