With the term logistics i don't mean only the computer of the helicopter, a helicopter and generally every machine is made from thousands of smaller and bigger parts and each one has a different part in the logistic's system. I don't think that Apache shares the same parts with Cobra and even more T-129 don't share the same parts with the other helicopters.
It's not even a matter of money only, money is only the mean to buy the equipment, there is a whole system of storage and management behind everything in service and more systems in service means more complexity. that's the nightmare i refer to.
Also about what you said of "Apaches will get the same treatment", meaning that they will share some components of T-129 in them, that means that this will need some extra time and money for such things to be implemented in the Apache. So if Turkey buys them now, and if we look in Greek Army's example, i don't think that the first will be delivered before 2011. The Greek example shows us that Greek Army signed a contract for 12 helicopters in 2004 if i remember well and the helicopters were delivered in 2007, that's 3 years later without lots of changes in the configuration of the helicopters.
I am also wondering what might happen with those helicopters after T-129 come into service, will Turkey return them to Boeing?
To tell you the truth i don't think it's possible to see Apache's in Turkish service.