Not sure about postage prices in other parts of the world - I'm in Australia. Also not sure how reliable postage to Turkey is ..... Having said that, from my experience -
Having bought a lot of kits from all over the world, I have found the best sources to be Model Hobbies in the UK (10% cheaper than Hannants) and PlazaJapan in .... Japan. Both offer very good prices and very reasonable postage, take paypal and are reliable. Plaza's range is somewhat limited, but if you want Hasegawa, Fujimi or Tamiya that's the place.
Try to buy kits from their origins - that is, don't buy a Japanese-made kit from China, or a Chinese-made kit from Japan.
The US stores are pretty much out of the picture because of high postage costs, at least to me Down Under anyway.
Lucky model are very hit and miss with stocks, and you can wait a LOOOOONG time for something you ordered to come in, and you have to pay for it WHEN YOU ORDER IT so they've got your money. No Paypal either, last time I bought from them. Occasionally they have $2 surface shipping sales for orders over a certain amount, and that may be worthwhile for you. For a Chinese seller, Hobbyeasy are much better. I don't think they stock stuff, but rather provide a seamless link to suppliers who have what you want in stock.
HobbyLinkJapan have a great range and allow you to order stuff and they store it for up to 60 days so you can add to the order later and minimise postage per item. Not as good since they went over to their new website and payment system a year ago (or is it 2? ), but still worth a look.
Also, try to build up a list and buy multiple items from the same source at the same time, and you'll save heaps on postage.
Good luck, and happy buying.