We used 1 eVisa yesterday (as mine was still current) as we flew via Istanbul and just in case there were queues or we were late when we landed at 5am as we only had just over an hour before our connection to DLM.
All very easy to buy/print etc, but on top of the £12.24 converted rate, HSBC MasterCard charged £0.36 for a foreign transaction fee.
Not sure if that is a % or set fee.