Are there any relatively cheap (possibly reusable) products out there that look like fondant that I can use on my cake dummies? I don't mind decorating in real fondant and buttercream. I just have a hard time spending $20 on a bucket of fondant, then essentially throwing it away.

Maybe playdough? Model magic? Clay?

I think you'll find that most of those "replacements" are more expensive by the pound.

There are many recipes on the site for MMF (marshmallow fondant) and it can cost less than $1/lb.

My solution is to buy Wilton fondant with my Michael's coupons. I love the workability of it. That runs about $2.25/lb. and with dummies, you can usually use somewhat thinner coatings because the surface is so regular.

HTH
Rae