Maybe this information is getting crossed with residency multiple entry visa, the one you purchase from the UK allows you into the country but once you leave Turkey it becomes invalid, the cost is approx £207 (maybe this amount is now £216?), The same can be purchased in Turkey (Emniyet Mudurlugu Yabancilar Subesi)apply within 30days of expiry, this one is multi entry.
just a foot note, all those that have a home in Turkey and visit often but don't have a residency, one partner to buy the six month residency then you can have the telephone line installed with ADSL once the residency has run out the telephone and ADSL will still be there, as long as you set up the DD to pay for the standing charges.