Just to get this out of the way, being dishonest is always immoral. Your example with the disabled person, and with selling GNU software, is an example of dishonesty (in fact taken separately, they would be two examples of dishonesty).
But, this original question, of what is an appropriate price for a product, I’d love to address in depth:
Is it moral to sell a product or service when you know your customer could get it somewhere else for less?
I work as a freelance web designer and programmer. Sometimes, I charge an hourly rate or a fixed price for a given service, and let the client decide if my prices work for him or not. Simply because that’s what a lot of clients learned to expect, and they’re not willing to do things any other way.
But, whenever I can and I believe it is worth my time to do so, I prefer to instead have an in depth conversation with the customer about what he needs, and how much value he will get out of my services. And then, instead of calculating how many hours of my time the project will take, I charge a fraction of that estimated value.
The reason why this works better is because it prevents bad deals, on both sides. Most importantly, it prevents me from either under-selling or over-selling my services. If instead I just charged a fixed price, my only direct feedback on whether the price is correct would be either having too many clients, or not having enough of them. Either way, I’d be losing money because my pricing sucks. And second, it prevents the client from buying something that isn’t worth it for him. It’s not out of the ordinary for a client to realize, midway through the conversation, that he doesn’t need all the shiny toys and fancy features he thought he did. And then he’s happy that I didn’t just sell them to him and sent him the bill, the way someone who works with fixed prices would (because why would such a person care whether the client needs or doesn’t need his services? he gets paid either way).
And yes, this does mean that client A and client B, who both want a similar kind of product, could end up paying significantly different prices, simply because client A has a greater use for the product than client B. However, things do even out, in the long run. When client A and client B end up both needing me again, and I only have time for one of them, guess which one of them gets my limited time, and which one of them gets to go out browsing the wild prairie known as the online freelanced industry, and hope to find another competent programmer to help him out.
Ha ha. I found an example of something being for free in one place but for a price in another:
free:
https://www.youtube.com/watch?v=XPSGMbqEGU0
not free: https://estore.aynrand.org/p/165/principled-leadership-mp3-download
That’s not the same product. One is streaming video, the other an mp3 available for download. Yes, you can rip youtube vids to mp3, but that is technically a violation of copyright law. Not that it would make a difference, even if that mp3 was available for free download on Notre Dame’s site.
ARI has a separate website, that provides a bandwidth they pay for, which allows these downloads. If they wish to charge a fee for all downloads, even ones that are available for free elsewhere, to pay for the site maintenance and bandwidth, that is fair. It’s a very similar example to how bottled spring water in your local convenience store is not the same product as water out of a spring in the woods, half way around the world.