I'm not so sure that is always true. I remember they flooded the market with 1/55 so much that they cut back by the time max and mirya were out which caused a shortage of those, hence the $300+ price tag of them new later on.
Also chogokin roy focker is really easy to get and costs less than most of the other chogokin. I thought they would be pretty balanced in price but I'm just guessing here but I think they flooded out the market with that one particular valkyrie.