Recently, I wanted a product to take the chlorine out of swimwear. The products on offer were fairly expensive -- typically $5 (plus shipping and handling) for a 2 ounce bottle of dechlorinator. But I discovered that the mystery ingredient is sodium thiosulfate, so it was a simple matter to find some other product that uses the same ingredient.
As it turns out, it is also used as a dechlorinator for water for pets, and the cheapest source is R-Zilla's Aquatic Reptile Water Conditioner which costs $10 for 8 ounces at my local petstore. So now I am using this to take the chlorine out of my swimsuit.