Turkish Airlines flies from Varna to Istanbul once daily. Alternatively, Burgas Bus operates a bus from Varna to Istanbul hourly. Tickets cost $8 - $10 and the journey takes 2 h. 2 other operators also service this route.
From Varna taxi to Varna airport, fly to Istanbul airport, then Metro to Istanbul. 1 h 45 min $134. From Varna bus to Burgas South, bus to Otogar, then Metro to Aksaray. 8 h 14 min $33. From Varna bus to Istanbul. 9 h 15 min $24. From Varna bus to Otogar then Metro to Aksaray. 9 h 46 min $21. From Varna drive to Istanbul. 6 h 8 min $72.