That is a Cute item and have seen many, always seemed useful for user. :)
Now for opinion; where to sell, Hospital Gift shops a great idea, medical supply store, these may want commission, ask if you can put your contact info by the display. See if Senior center and Indepedent Living homes will let you post a notice that these are available, can always donate 1 oe 2 to see if can get a buzz going. Don't think 20-30 is out of the ball park for pricing. Sturdier base fab, denim, poplin, upolstery (samples) with the upscale Fabric as trim. Found some upolstery fab at WM 60" for 1.50 yd.
Keep in mind all will have to be a little different colors etc. Hate to see a who's walker is that argument, think that sometimes happens anyway!! (gotta add some interest even in at that age and situation)
Good Luck !!! Happy Sewing :)