They need to realize that developers get very little per copy. Apple takes 30% of that 99 cents you pay. How many apps would you have to sell at 99 cents each to make enough to survive and make it worth your time to keep building that app and adding features, etc.
That's not and never should be the customer's concern.
As the customer if I see a price tag on a product, all that matters to me is the price on the tag. It's up to the retailer to make sure the product is appropriately priced with necessary margins to cover the costs of selling that product. If all the retailer gets in the end is a negligible amount of money, that's the retailer's problem, not mine as the customer.
The other problem I have with this argument is that it goes the other way as well: developers must acknowledge the cost of putting up software on sale on the App Store in the first place. Much like putting up products on store shelves doesn't come for free, developers have to recognize the value of visibility on the App Store, for which Apple takes a 30% cut per sale. Whether 30% is too much is beside the point: developers must abide by Apple's terms before selling anything on the App Store. If the developer agrees to the terms of the contract and knows beforehand that Apple takes a 30% cut per sale, it's the developer's sole fault if they're not making a living with a 99 cent app. That's the cold truth no matter how you look at it.
Finally, there's the culture of economics to consider. How much a customer is willing to pay for a product is defined by the market, as well as the qualities of the product. Whether we're talking about software or tangible goods, the same principle applies. Because developers have run with the 99 cent app idea for so long, customers have been trained to think apps are worth 99 cents. Any app with a higher price tag will have less downloads than a comparable 99 cent app. You can't blame customers for not willing to pay more if the market has trained customers to believe apps are worth 99 cents.