In August 2008 I was caught close to Antalya at 105 km/h and I was fined for 100 Euro (It had to be 130 but it was reduced to 100 by the officers themselves).
I paid directly in officers' hands, but they issued me a regular receipt with their signature and with mine, reporting all the datas of my passport and motorcycle: a regular ticket, I mean.
But I know a couple of friends of mine that were fined in central Turkey last year, and who were told by the cops that they had to pay at the border when exiting the Country.
Somehow, the custom officer at Turkey-Bulgaria borderline did not mention any speeding record from his computer: they remained silent, and finally got back to Italy without paying a cent.
Nick and his 2010 Yamaha XT1200Z Super Ténéré