Data, not opinion. I've checked around a bit since Michigan legalised pot for recreation as well as medical use.
The going "street" price for an eighth of an ounce (about 3 1/2 grams) of good quality pot has been about $50 ( no tax, of course) for a few years. We have two stores open and two more coming in a few months. The two existing stores are selling 3.5 g of tested and certified and guaranteed quality for about $25 including sales and pot tax -- and that's before discounts for having a med card or other reasons, so that eighth ends up costing a bit less than $24.
And everyone thought that legal pot was going to cost more than black market. HaH!