Porsche are one of the few that manages the supply vs demand position well. Mercedes and BMW have both created a glut of production and effectively used finance options, leasing and the like to sell more cars but this has the effect of affecting desirability as well as residuals. One look at the value of a 3/4 year old S class or & series shows you how badly they have hampered their value proposition. BMWs, Audis and Mercs are no longer exclusive or high end, with a niche for every occasion and some that don't exist at all (5 series GT, CLS Shooting Brake or X6M anyone?)
Porsche has managed in increase production without devaluing their brand identity and they seem unlikely to do that any time soon. Until they do, we won't see discounts to the leasers and hence we won't see cheap Boxter or Macan leases.
Ferrari, in the other hand are using Maserati as a way of increasing production of high end machines as they continue to protect their core brand with limited production and invitation only specials. They continue to struggle to find a strong market place for Alfa which is a shame as a luxury Alfa saloon could be great. Instead they're making the lovely, lotus-esque 4C in small numbers and the average Guilietta and Mito (sorry if you own one, no offence intended!). At least they have got out of the habit of building large, expensive Fiats that don't sell and stuck them with cool small cars.
Maserati are playing a dangerous game as they really need an Alfieri etc on sale to counter the devalued identity that the Ghibli will and is bringing.