iMac = prosumer![]()
The iMac is NOT an ideal prosumer machine, although Apple is pitching it as one. First, a prosumer would nominally want to pick their own display. Both in terms of size/resolution, and also choosing whether they want faster update speed, better color spectrum, whatever. They will spend the money they feel is required to get the display they want, and will want to keep it when they upgrade.
Second, the supposed prosumer is the sort of user who you would expect to want to add a second HDD later on, upgrade their GPU, and fo other various system updates and modifications after purchase. The new iMacs don't even have a user serviceable HDD.
Lastly, a prosumer is NOT the sort of person who will put form ahead of function, and as such shouldn't have to settle for a laptop GPU, a laptop CPU, and a laptop optical drive, just so they can have a slim AIO machine.
Basically, Apple doesn't offer a prosumer machine. They have a very high end line of pro computers, and a large array of standard consumer boxes based on price range and whether you need a new display or not.