I’ve reserved private transport to/from the city center with this company in July and August and will report back. They promise a nice Mercedes or minivan, images show some really nice ones.
cost: 50 EUR per transfer, not per person, payable in cash in person
I’d usually take the Havaist buses, but with a group of people, this transfer option makes sense.
https://instagram.com/istanbulnewair...d=7l1m5ftysx6l