Looks like a cash grab.
I will subscribe to @Bodigrim 's opinion here:
Could we as a community have a bit more good faith in each other, unless proven otherwise? Come on, 49 € are unlikely to recoup resources spent and ongoing in the foreseeable future.
In fact, see @jagajaga 's (Serokell CEO) reply here:
The exam fees will never cover all the resources we have invested in this project.
If I may add my personal opinion: this is absolutely not a scam.
You may not have heard of them, which is reasonable, but Serokell is a legitimate company - I’ve worked with them in the past, and so have many others.
One of their team members, Vladislav Zavialov, is part of the GHC Steering Committee.
Through him, and other current and former team members, Serokell has made many appreciated contributions to GHC and the wider Haskell ecosystem - this last qualitative judgement is my personal opinion 
I haven’t been involved in the Haskell community; however, I would still recommend this to any prospective or junior Haskeller.