A lot of wrong stuff here.
First of all, EUR 30 in the mid-80s is equivalent to roughly EUR 55 today due to the effects of inflation (these are approximate numbers for countries like Germany and the Netherlands). Inflation was slightly higher in the US, so a larger increase in dollar prices was necessary over there to compensate producers for rising input prices.
Second, I don't think MSX games are really representative for what OP is referring to. MSX was never really mainstream in the US and Europe.
Third, production cost have risen tremendously, yes. But a good chunk of the cost of producing a video game is fixed. And since the market for video games has grown tremendously over the last three decades, those fixed cost are distributed over a much larger number of games sold, therefore facilitating lower video game prices (in real terms).