Per buying tickets to Topkapi & Hagia Sophia

No this is the correct web site.Click on bilet then click on e bilet and there is a drop down menu(müze seç) for the sites covered.It clearly says 15-30TL.Hagia Sofia is 30TL and Topkapı Palace is also 30TL.Please note that for Topkapı Harem section there is an extra ticket needed which is 15TL.
I think maybe you clicked on Müzekart which is a card for museums outside Istanbul.
I must also apologise to every visit to Turkey that this web site is only in Turkish.I cannot believe that such an important thing has no English menu on it.A HUGE blunder by the tourism ministry on their new web site which I hope they will put right soon.

Ahaa,look what I found for you and in English too :)) Prices are the same btw.
http://www.biletix.com/museum/TURKIYE/en

Thanks a lot.
I assume online ordering has the benefit of avoiding the queue for the Instanbul museums, is that right? For the Goreme musuems I guess there is not much benefit in pre-ordering, is it?
Cheers, Herman

Perfect! Thank you so much for your help! & yes, I've noticed all the websites are in Turkish, but that's where Google Translate is amazing! 😀

The English page on the government website - https://www.muze.gov.tr/en/purchase?t=5

David you amaze me!Where/how did you find this?I looked all over the homepage for a language menu but couldn't see one.
@Hermanleenders;yes,the biggest benefit is being able to walk straight in rather than queue.That is a huge bonus as queues for both Topkapı and Hagia Sofia are very long now almost all year round but especially from April through to November.
In Cappadocia ....no I don't think there is a great benefit.Queues do form but not on the scale of Istanbul,i.e you may need to wait a few minutes to get into a particular cave church to allow others to come out but that is all-not an hour like T.P! .

Thanks both!

I too am trying to buy tickets online but I read somewhere I can't actually just present my email proof that I purchased the tickets but that I have to go pick them up from one of several locations in Istanbum. Is this true? Don't want to give my credit card info until I understand the process.

Download and print off the e- ticket and present that at the entrance gates,that's all.Perhaps you have got mixed up with the Museum Pass which one does need to collect from a particular point.