Hm, why? As iStar wrote early in this thread, the fees that are paid for American or Canadian tourist visas are used to cover the enormous costs of making sure that all those applying for tourist visas, globally, intend to respect the limits of those tourist visas and not to stick around because there's not much opportunity back home. Argentina doesn't have these costs. And, as you said, Americans (and Canadians) are coming down here to "stretch" (i.e., SPEND) their dollars, not because they're desperate to get their hands on a few Argentine pesos.
Are you, perhaps, as Denver described earlier in this thread, allowing pride to displace reason? When Argentina gets its economy in order and isn't viewed as a potential source of "economic refugees," it should rightfully be given US visa waiver status, Argentines should get US tourist visas for free and the US can stop paying for it's huge visa operation here in Buenos Aires. For now, however, this new "reciprocity" fee is just another money grab by the Argentine government. But, I suppose, with all of the things that are subsidized here (including politicians' vacation homes in Punta), the government needs the money.