Commodore - A Company on the Edge by Brian Bagnall covers the Commodore side of the "Troika of 77" (Tandy / Radio-Shack, Apple and Commodore" who made up the bulk of the volume sales in the early home computer market).
Commodore's ongoing hunt for vertical integration and their huge margins in periods were definitively impressive, and the numbers you cite probably indicate their peak margins (at least in percent)
But Commodore rode waves - they kept getting close to crisis and then rode through it once they had their next temporarily high margin product for a while, then their margins would get squeezed either by their competition or their own decisions, as their product lines were aging and they were too slow to replace them. It happened with the PET, the Vic-20, the C-64, and eventually did them in with the Amiga.
With the Vic-20 and C-64 it was actually Tramiel (Commodore's founder) himself that dropped margins massively to force Texas Instruments out of the home computer market.
The $595 price lasted for a very short time, as Commodore went through wave after wave of slashing VIC-20 prices (eventually to under $100) and C-64 prices. With a $100 trade-in offer, the C-64 dropped as low as $300 in 1983, and at Spring CES they dropped their prices to dealers to $200-$250...
The result was that TI lost $100 million a quarter, and was forced to quit the home computer market entirely. Commodore was still making money at those prices, but obviously their margins had been slashed massively, and so again R&D suffered.
Towards the end their vertical integration was pretty much gone - Commodore Semiconductor Group had seen so little investment that they were not competitive at all, and more and more of Commodore's chip manufacturing was done by partners.
BTW, I had a TI-99 4/A. It was an okay machine, but not part of the troika, and I think I was the only kid I knew with one. I do remember when TI decided to get out of the business and do a fireside sale of all its inventory. The computer which had been so expensive ended up under $99. But I still couldn't afford the expansion box which was needed to handle a disk drive.
Also, while it's been covered in HN before, you might be interested in Jimmy Maher's ongoing series on the history of interactive fiction, including how it's tied into the mainframe hardware of the 1970s and micro hardware of the 70s and 80s. It's at http://www.filfre.net/ .
That was probably the biggest margin as Commodore was fully vertically integrated.