This problem not only isn't unique to iOS dev work, it's not even unique to programming. Any custom work, from carpentry to bespoke tailoring to artwork, is more expensive than most people expect, even when they account for custom work being expensive. For instance, I knit, and have been asked more than once if I'd accept a commission (for, say, a pair of socks)---and when I decline, and say they couldn't afford it, they almost invariably throw out a number like $60 or $80, very expensive for a pair of socks but a small fraction of minimum wage for something that could take thirty hours or more.
The problem is that so much of what we buy is mass-produced that we forget just how expensive person-time is, especially creative person-time, since for most modern products this gets amortised over hundreds or thousands or millions of units. Even user-facing software has this issue, since the programmers do their work once and then the marginal cost of each additional copy is pennies or less. But custom work? There the cost is borne entirely by the one commissioning the work, and if it's an individual, or a small business or startup that has never had to purchase enterprise or custom software, they simply have no analogous experience, with software or anything else, of bearing the entire cost of everything.