I think it is a $1500 option in most RV's, and not worth it to me. Sometimes I don't even like doing a "LOT" of laundry at home, but rather take it all to a laundrymat and put it into the 3-5 large machines that tumble the clothes, getting them cleaner, with less damage than a typical upright washer.
And best part is the huge gas dryers dry everything in about 20 minutes. Anything still a little wet goes into one dryer, and that finishes everything, while I am folding and hanging my clothes. So all is done in about 3 hours from the time I leave home until I am hanging everything up at home again. . .
Sure it is OK to wash a few things, but I would rather pack 2 weeks worth of clothes, and then wash them all at once. Usually once I am home. . . You probably have to have full hookups to run the washer - even if your tanks are large enough, as the washer in most systems will not empty into the grey tank. One sticker that I saw in a closet with washer hookups (but not the washer option) says 'grey hose must be connected to run washing machine'.
Good luck!
Fred.