"Free markets" are rarely free of constraints, either put into place by politics, taxing policy, and/or corporate efforts to control the market, e.g. monopolies, cartels, location, restricting supply, etc. On the side of the consumer, one has consumer "unions", discussion forums, online buying, etc.
If one is locked into Pentax by the lenses one has, then to a limited degree, Pentax has control over the prices they charge. In the broader market, if the prices are too onerous, then Pentax owners can choose to move to another camera system. As long as we have sufficient numbers of camera makers, then there is competitive pricing of cameras. One has to be concerned when too many camera makers go out of business. Or too many suppliers of key components, e.g. sensors, go out of business.
While the goal behind establishing fixed profit margins to encourage local stores is admirable, there are pitfalls involved. In the process of getting more local stores to carry Pentax products, the base population may decide to move to another brand. So a manufacturer may have lots of product on local store shelves, but fewer customers to buy them. whoops
Plus, one can't change culture or build new brick and mortar stores overnight.