FifteensAway, thanks for taking a look at my blog! No, they are not too expensive as they cover quite a large amount of area. The most recent purchases were at a craft store in the US called Michael’s, though they carry them at Hobby Lobby too, but for a bit more. Luckily on line coupons can easily be had for both locations. A similar substance can be created with white glue or caulking with sand, Railroad ballast, and paint, but it’s not as thick and drys much faster giving you much less working time for a large batch.
PS - I’ve enjoyed your posts and collections for quite sometime sir!