Instead of buying all your molds, you can use old or about to be garbage/recycling containers that you have. Important information is that if you use a plastic or acrylic container it should be easy to deform so that you can ummold your soap easily.
Another idea is to make your own molds! I still haven’t made any but I am planning on making:
As soon as I begin to make my molds I will update my experiences!!
Update May 2017:
I make my own acrylic soap molds!
I use acrylic sheets that are cut in my laser machine with drawings that I made myself.
If you would like more information go to my webstore: