How much did this project cost
Well, I had most of the materials already, so it didn't cost me really anything, but if you didn't have anything...
StyroFoam $10
Great stuff expanding foam: $10
Tape $5
Fiberglass resin $20
Fiberglass chopmat: $5
Bag of Grout: $10
Epoxy sealant: $30-40 (you could seal it with polyester or sweetwater epoxy or something for cheaper maybe)
3 colors of krylon fusion: $5x3=$15
so like around $100 if you don't include stuff like gloves, paint brushes, hot glue, etc.