Peace to you too (sincerely), but you're off your rocker!
However "legal" the herb trade may become in the USA, it will unlikely be completely unregulated like a piece of tech' or a T-shirt made in Chinese or Bangladeshi sweatshops, so there's no parallel to draw between the sectors. The number of LICENSED, large-scale producers will be controlled and most likely taxed to high hell. It's just the way it is for now and you just know that somewhere along the line the FDA will sink its teeth into the industry if and when it is nation-wide. This is not an argument about archaic prohibition laws, which, as you stated, were brought in under false pretences. It's a conversation about how freely people within the commercial herb business will be able to operate. Rightly or wrongly, it is unlikely to be a free-for-all like the cell phone or textile industries in the foreseeable future. As such, there is likely to always be a black market.
Back to Amsterdam again if you'll permit, have you ever been there and found cheap, high quality herb? Most (in fact almost all) of the locals still buy from dealers on the black market and while they don't pay tourist/coffee shop prices, they're a long way off $50 or even €50 an ounce. Probably over €200 for the high potency (top shelf) sensi', unless buying from a good friend. So I can't see how what you're saying would play out that way in the US when it hasn't elsewhere, certainly not while it remains outlawed in many parts of the country.
Lest we not forget that the USA is also capitalism's shining torch and the unlikely to be a place where a popular product is knowingly undersold. It's all very well talking about increased competition in the market place, but prices tend to be quite carefully controlled in most industries. You don't find gas 30c/l cheaper at a gas station that one a mile down the road. Herb will be no different. It's a commodity, just like gasoline, fillet mignon, beer, cigarettes or any other product and its producers/distributors/retailers etc. will seek to exploit it to maximize their profits. Business is business. Stop being naïve.