> But when I fly out of or into EU, all passengers upon deboarding are herded thru immigration gates,
There are no
border formalities within the 26 countries which make up the Schengen Zone (most Schengen countries, though not all, are also in the EU). So if you fly into any
Schengen country in transit to another Schengen country you will
go through border control on that first arrival. All arrival and departure data (whether by land, sea or air) is recorded on a system shared by all the Schengen countries.Turkey
is neither in the EU nor the Schengen Zone, of course. >Since I'm going to have to pickup luggage and return through security will I need visa?
Yes, of course you will. Whenever you go through border control, collect your bags, go through Customs and then need to go back through security you have gone landside
. Once you are landside you have legally entered the country and must therefore abide by the entry requirements of that country. That's the same everywhere, including the USA.
As a US citizen (I assume) you can just get a Turkish e-visa online using the official site I've linked below. It will cost you 50USD and allow you multiple entries during its 180-day validity. https://www.evisa.gov.tr/en/
I don't know where you've seen mention of a '$10 visa' but that information is long out-of-date. I paid roughly that amount for visa on arrival to Turkey but that was well over 10 years ago. Visa on arrival has been largely phased out and replaced by e-visas for eligible citizenships.
Depending on which Turkish airport you fly into you may be able to get a visa on arrival but
queues can be very long indeed and it's not something I would risk doing if I had to catch an onward flight...and getting visa on arrival is more expensive than an e-visa anyway:http://www.mfa.gov.tr/visa-information-for-foreigners.en.mfa