When they say "dead sand" they mean not live sand which is what comes packaged with water, bacteria, microorganisms in the sand.
Theres dead sand at the LFS, the sand from home depot would also be "Dead" .
the sand people use is called southdown but its very very hard to find nowadays. With playground sand you need to make sure you wont be getting silicates - theres a test you can do with.. vinegar? If you pour some on the sand and it fizzes i think you're good to go (not 100% sure on that so you should definitely do some research first)
Sand at the LFS is probably give or take $15 for a 30 lb bag in my experience.