There has been a massive slow decline in E46 m3 for sale. I keep an eye on the market fairly regularly and you might see a decent one coming up for sale once every three/six month. They are still the same price as when I bought mine 3 years ago.
This is surprising as insurance/road tax for these cars are insane and I thought more people will be selling theirs. Altho with the amount of money/time/sweat I ve spent on mine I d rather keep it off the road if I couldn't afford it.