Most washers I've bought actually come with a set. Now if they are covering their own liability, they should just factor that into the sale and do it. If they are trying to make you pay for them at a price that is above what you could get a set for, then I'd say it's a scam.
I'd recommend changing them every few years. I'd also recommend the auto shut-offs as I've seen the damage having one break can do.
To a small child, the perfect granddad is unafraid of big dogs and fierce storms but absolutely terrified of the word “boo.” – Robert Brault