what's this "bmw tax" you speak of?
SS exhaust for a Camaro: $250
same SS exhaust, but in a BMW box : $2500
That, also known as Corvette tax, etc., depending on the car. Basically ripping people off because they have money to spend on expensive cars figuring they will write a blank check for a $10,000 part without thinking twice when that part costs $1,000 for every other car in the world.
How does a plastic tube and a $10 filter cost $100 for one car and $500 for another car? That phenomenon of making a fixed production cost item scale in retail price as a percentage of the price of the car it's sold to go on is known as the "BMW/Corvette/Lexus/whatever tax"
Better off modifying what you have for more power by throwing a supercharger or turbo on your I6 (even still with the BMW tax on those parts) than paying Dinan $50,000 to throw a chip and some spark plugs in a $25,000 engine for you and paying a "BMW certified" mechanic 5x the standard rate to install it for you. Or you can just pull your factory crank out and have a machine shop turn it to whatever stroke/rod journal size you want for <= $300.
The people who could afford these engine swaps you're talking about on a brand new car aren't bothering with $50,000 BMWs unless it's a dedicated track toy. Those who do have $50,000 BMWs and drive them on the street are middle class folks who work to pay the bills and still don't have $25k to throw away on an engine swap for 40 more HP, on top of their $1000 a month car payment, when they can spend $6k on a supercharger and get 100+ HP. Ok I admit I didn't even look to see how much that crate motor costs, but I can't be too far off with the money Dinan charges for things like "stage 10 tune and plug wires".