In a nutshell, you get what you pay for.
But seriously, Gokalp is super responsive and he fixes any issue really quickly.
The location is brilliant! You'll be close to everything you need. You should know that Kadiköy is the actual heart of the city, even though maps would disagree. Besides, you'll be only a 20-minute ferry ride away from Istanbul's geographical centre if you feel like doing touristy stuff.
The place was clean upon our arrival, and had everything we needed. It's fairly small, but it's still worth the money paid as compared to other options in the same range.
Thanks!