Interesting enough, Suprep® is made with very simple chemicals that are readily available, and frankly, cheap. It is just another example of Big Pharma ripping us off.
35 grams sodium sulfate (Glauber Salts)
6.3 grams Potassium Sulfate
3.2 grams Magnesium Sulfate (6.4 grams if using Magnesium Sulfate Heptahydrate, which is what Most Epsom Salts products are).
Each dose of Suprep is half of the above.
Sodium sulfate can be purchased on ebay for about $8 for 454 grams
Potassium Sulfate can be purchased on ebay for about $10 for 454 grams
Epsom Salts are about $2 a pound from you local drug store,
So the actual manufacturing cost of Suprep is under $1.
Another product, Ferrings's Clenpiq is sold under various names elsewhere I the world. In the US it is about $145, in Australia the same two packets are about $8 at current exchange rates, and in Canada for a small fraction of the US price.
The fleet products are a little more complex because there are actually two different sodium phosphate products in it. Monobasic and Dibasic. Monobasic is NaH2PO4, Dibasic is NA2HPO4. It isn't clear to me that there is a lot of difference in between Monobasic and Dibasic as far as effects are concerned.