Funnily enough, I was quite surprised when I went to buy tiles as they ended up being less expensive than the repti-carpet we'd had previously that needed to be replaced every now and again. And, they were certainly less expensive than that useless bag of calci-sand we had in the viv for all of one day,
way back when.
We spent all of $10 for a permanent (AND LOVELY) substrate at Lowe's hardware: 3 - sq ft tiles, and 6 - 4" x 4" covered our 40 breeder nicely. I just made sure to get a tile with some texture, and a sandy feel for gripping to keep those nails down, aye yaye yaye! And it's helped tremendously. I have fewer beardie scratches these days!
Good luck!
Em