Yes, the punchline of the joke is that synthesizing pseudoephedrine from meth is more convenient than buying Sudafed after the law on restricting sales ostensib

Yes, the punchline of the joke is that synthesizing pseudoephedrine from meth is more convenient than buying Sudafed after the law on restricting sales ostensibly to reduce meth production. i.e., the law didn't do much to halt meth production but did put a bunch of barriers around a useful drug _and_ promoted the use of phenylephrine instead, a useless drug in pill form. A huge net negative.