I've travelled with Aegean multiple times while having minor differences between names on ticket and names on identification documents. For example a double consonant in Greek is often translated as a single consonant in english, an "i" is often spelled "y" or vise-versa etc. etc. We've even had cases where the new passport had different spelling than the old one regarding the above. Never have we ever had an issue at the airport (I've also once mistakenly entered/selected "Mr." instead of "Mrs." for my Mrs., but that's technically even less of a mistake, since they shouldn't be asking about gender in the first place (they only do it in order to be able to address you properly).
If the flights were with Aegean, within Schengen and it was just one letter, I would have certainly gone for it, especially if that flight was originating in Greece (hell, we even currently hold a national ID and a passport for the same person that have different spelling on both the first and the last name!).

Anyway, I don't know why the comment from Xandrios , even though "liked", seems to have gone unnoticed... 20 EUR is the fee for using the call center, not for changing your name, but for whatever the reason was (where they had to take any kind of action, other than simply passing on information to you). If they had to charge for editing the name as well, it would have been 20 EUR + whatever they would have charged for that. I think the only argument that would make sense would be, that Aegean could have (as a policy) allowed for a single correction of the passengers details within the first 24 hours after booking online without using the call center (but one could also argue, that such a policy should exist with regards to all matters, like cancelling an award ticket online etc.), but other than that, it's only on rare cases, where a technical error won't allow someone to use a service, that would otherwise be available online, that Aegean would waive the call center fee (and like I already wrote, it's just a matter of airline policy/pricing and if you're using Aegean enough, you'll probably be glad that there's only that 20 EUR fee and not a complete list of different "call-center-fees" according to what gets done/changed, since that would result in huge increases on prices for services, that are now considered to be very cheap compared to other airlines).