What do you think about this situation?
You are probably referring to digital products that have an initial development cost, but no or negligible transport and manufacturing costs. Buying a digital game on Steam is a good example of this (this goes for films, ebooks, and music as well).
Game prices on Steam can be based on the GDP of your country, because if they used the same prices as in Western Europe or the US everywhere, a lot of people would not be able to afford the games. For a game developer on Steam a lost sale means less profit, whereas a sale, any sale, means profit — even if the price was heavily discounted — at no, or almost no, additional cost for the service rendered. Not everyone does this though, because that is how a free economy works. If a game studio thinks they can sell more games in Turkey by lowering prices there, they will probably do it.
On the other hand, if someone is selling an ebook that no one else sells, and they know that you are willing to pay the full price even though it costs you more (relatively speaking), then why would they lower the price? They are a business, not a philanthropy.
I'd say you are right to point out that it costs more-or-less the same to deliver digital services like Coursera. But perhaps because the content was largely produced in the US (I'm assuming it is) their costs align with US wages and costs.