Ken, if the website is based in either the UK or Europe and would normally take your payment in either GBP or Euro but allows you to pay in lira, like Trivago or Travel Republic etc. they will simply use a currency converter and so you will pay more lira while the currency is weak. You might get a deal from Turkish airlines but because the currency is so weak, they could be getting hammered for fuel costs and landing charges in the same way that anything imported here will be costing a lot more money if paid for in lira.