I fully understand how expensive this equipment was, and how to take into account inflation, etc. But...If you were buying a Macintosh 128/512K, you most likely had an awful lot of money to spend on what was essentially a very pricey plaything. (Yeah, I'll probably get crap for that). Apple's marketing highlighted young white men, but I seriously doubt those kind of people could ever have afforded a Macintosh with accessories. For the first year, there was very very little software available for it. No backwards compatibility with the Apple II meant it wasn't useful for all those Apple II users.
It wasn't until PageMaker and the LaserWriter in '85, and then a year later, when we had FreeHand, and other programs, that the Mac actually started to get serious interest from people who wanted to get things done. I'm sure some people got by with MacPaint and MacWrite, but in reality the lack of software really affected sales during the first two years. Cost, however, probably not so much - once the Mac had this huge graphics appeal, businesses were going for it. It was much more a machine for the business world than a machine for the masses of people who just wanted a computer for less than $1,000. So, if you think about it, the people buying Macintoshes were unlikely to be sitting around thinking "ohh, ahh, umm, well that extra $500 for another drive is sure a lot of money."
Those who bought these machines were the early adopters of new technology - and they paid the price. It wasn't a "computer for the rest of us" when, with all the options, it added up more than $6,000+ in today's money. At this stage, the vast majority kept on buying cheap clones, Commodores, and Apple IIs. You can still spend silly money on Apple machines, obviously you're getting quite a bit of kit for your money, but you could spend $7,000 on a MBP with loads of options, extras. And if I was spending $7,000 on a MBP, I would not be hesitant to pay another $500 or even $1000 if it really speeded up productivity, like a second FDD would have back in the early days.