Ok children, lets crush up some sudafed pills, mix it with some battery acid, then some ammonia, and whatever the hell else we can find under the sink and in the bathroom and mix it together, cook it for awhile (btw the fumes cause brain damage, loads of fun!) then well snort it untill were digging at our skin like monkeys digging for mites, sounds like fun huh?!.........phhh.
Salt water can be made from lye (drain cleaner) and hydrochloric acid (very corrosive acid).
I don't know what they taught you about meth in school, but its made from reduction of ephedrine and for large scale synthesis it would be impracticle to use pseudoephedrine containing OTC medications. There are many methods for making meth and it is pretty easy to do but it isn't like these kitchen chemists are using random chemicals, most have to have at least a basic understanding of what they are doing.
It is correct though that meth on the streets is impure, users cannot be sure of its potency (it is like you couldn't tell beer from hard liquor) and it would be better off legalized or allowed for doctors to prescribe to addicts since they are obiously going to use it anyways. This would also keep it out of the hands of teens.
Another part of the problem is that the overwhelming majority of schools drug education programs call for teaching abstinence as opposed to harm reduction.

If you want to look at it chemically you will see that methamphetamines come in two flavors or isomers dextro and levo, dextro being several times more potent. d-methamphetamine is what people on the street want although street meth usually turns out to be a mix of both isomers as well as the precursors psuedo/ephedrine. l-methamphetamine is found over the counter in small quantities such as in Vicks Nasal Inhalers but the active ingredients list has it as 'levmetamfetamine'. This is why we call it the War on some drugs, chemically these substances are very similar, they are isomers of each other and yet one has greater pyschological effects and thus is considered a bad drug.