So the point where the normal cost is $6.95 but it cost over $100 or $200 is not because the registrar is gouging you, but because the registry is charging the registrar minimum $100 or so, and then the registrar would also apply their own markup, which is pretty standard.
Also - all registrars are contractually obligated to send out multiple notifications to the admin contact email, and even though this wouldn't necessarily apply to .DE (because it's overseen by DENIC, not ICANN) - most registrars use the same notifcation workflow across all TLDs. Usually something like 90, 60, 30, 10 days and -5 days.
I will say that the rule in .DE that you can't renew past T-5 is pretty weird though.
But no matter who's responsible I think it's not right to ask someone to pay more than 19 times the price of the normal renewal just because they might have forgotton to renew. I'd have paid maybe €50 but €185 is borderline extortion in my opinion.
I can assure you, I have not gotten any kind of notification from Namecheap. I don't know why some people here are so insistent that I must have gotten them. I triple checked my email address at Namecheap and don't do spam filtering. If some mail isn't in my inbox it hasn't been sent.
 - https://tenebris.uber.space/article/i-fucked-up#price
I can't speak to whether the registrar sent you renewals or not. I did mention in another comment below that for some unfathomable reason my company (easyDNS) is the only one I know of that offers the functionality to setup an iCal feed with your domain expires.