It wasn’t easy, but I found some accommodation for the 7 Openismus employees who are going to GUADEC in Istanbul. The recommended accommodation (The 2 Hotel Golden Horn hotels) was booked out and I guess it has been for some time. You’ll be lucky to even get a reply from those hotels.
We booked two apartments (Glorya Penthouse Terrace and Glorya Tower View, in Beyoğlu near the Galata tower on the east side of the river.) from Istanbul Holiday Apartments, who are not cheap, but who speak (email) perfect English and are very straightforward.
I seem to have been completely wrong about the cost of accommodation in Istanbul, though it might be easier for individuals. I guess the city has boomed since my last visit. But over the last few years I have noticed that hotels everywhere have become increasingly unlike the places surrounding them. Most people who work in hotels could never afford to stay in them.