I just came across a fascinating video https://www.youtube.com/watch?v=7h4tepFbMso&t=78s which makes a coherent case - I don't feel I can pass a final verdict on whether he's right or wrong, but a coherent case - that the Mac was a mistake, that equal or better results could have been obtained by incremental development of the Apple II line without sacrificing backward compatibility. In support of this, he presents evidence that the Apple II GS at $1500 with color monitor, was a better machine than the Mac Plus at $2600. I'm not convinced by his claim that the 65816 had the potential to match the performance of the 68000, but the rest looks pretty solid.
What I'm wondering is, given that the Apple II GS by and large had better hardware, how did it cost less?
One obvious possibility is that the Mac did not actually cost any more to manufacture, but was sold at a higher price for higher profit margin. That seems a bit of a stretch. Granted Apple was reputed to have the highest profit margins in the industry, but the estimates I've seen for their profit margins as a ratio between retail price and manufacturing cost have been along the lines of 3x, maybe 4x; for reference, Commodore typically had 3x, which seems to have been quite normal. The Mac Plus, by that explanation, would have had to go far beyond that. And if they were going to bump the price of any machine to extract profit, why wouldn't they do that with the old cash cow instead of the new machine they wanted everyone to buy because it was hoped to be the future standard?
The ideal would be a table of cost estimates like https://en.wikipedia.org/wiki/Commodore_64#Manufacturing_cost for the two machines, but I haven't been able to find such. The closest I've found so far is https://web.stanford.edu/dept/SUL/sites/mac/primary/docs/bom/cost.html which is Apple's own estimates for the Mac, years before the fact (and seems to have been an underestimate by a considerable factor; why the underestimate, I don't know).
Are any cost data or credible estimates for these two machines, either absolute or relative, available?