I never really thought about it before, but everything on Google Domains is shown in my local currency (CAD) and I'm fairly sure I get billed in local currency. It's nice having everything in my local currency, but they don't do a good job of making it clear the underlying pricing is USD.
I think this person's case is a good example of where that can be problematic. Even if they had paid the correct price originally, they'd be seeing a 35% price increase because of the exchange rate. It's not unreasonable for them to have assumed the original purchase and renewals were always going to be in their local currency without fluctuation due to foreign exchange rates.
I skimmed ICANN's registrar accreditation agreement for info about pricing and it basically says registrars can price domains however they want. The registry agreement has pricing related limitations, so I think the intent is to ensure registries don't engage in abusive pricing with the assumption that competition will keep the registrars honest because registrants can transfer their domain to a new registrar if they're being mistreated.
That leaves this person with no recourse. The registrar (in my opinion) undercharged them and didn't do a good job of communicating the true ongoing cost of the domain. Transferring to a competing registrar doesn't help because the registry pricing for the domain is going to be around $700 USD while the registrant's expectations were set at TRY4360 ($230 USD today).
There aren't any great options to make it right either. The registry can't start discounting domains to fix mistakes made by a registrar, the registrar can't take a loss of $470 / year (at current exchange rates, potentially forever), and the registrant shouldn't have to pay $700 USD / year for a domain they thought was TRY4360 ($230 USD today). To make it worse, the registrant's expectations didn't get reevaluated until the bill for renewal came due and if they've spent a year developing on the domain it feels like extortion (to them).
It's also not fair to expect the registrant to realize they're underpaying. Price differences between registrars are enough for people to assume a low price is the result of finding a registrar with better pricing.
Google Domains isn't the only registrar that gives the impression domains are priced in local currency either. Gandi bills me in CAD and doesn't mention USD when I'm buying domains. Namecheap shows me prices in CAD, but bills in USD and it's not clear USD is the real price rather than simply being the billing currency.
Forget you know the registry sets prices in USD and go pretend to register 6b.dev on Google Domains. Select a foreign currency and see if you can figure out the price will fluctuate based on the exchange rate for USD. I'm not sure where the OP got the idea renewal would only be $12 rather than the TRY4360 they paid originally. There's nothing that left me with that impression.