I hear ya, but its already $8k for the M3LR vs M3P and was $10k earlier. When you actually think about what's in the car though, the cost should be way more than $5k.... at least when you compare it to the price jumps within the auto industry for performance cars and what's included.
Most people forget, for example, that the P comes with Brembo brakes.... that's pricey on its own. Then you have an upgraded rear motor and rims/tires that are larger and more expensive than the optional MYLR rims/tires... that cost $2k (just to go from 19'' to 20'', let alone the Ps 21''). Sport suspension.... rear spoiler, etc. There's just so much you get for only $5k. The rims alone would be a $3,000-3,500 upgrade over the MYLR rims if they were an option on that setup. The brake.... who knows.