Each side has pros and cons 100% correct.
Amazon charge a micro fee for transfering from the cluster to an FTP. you can upload any amount of data you want for free. Just to put that in the right perspective.
I do also note building your own farm there is not as easy as having someone else doing it for you and that costs, naturally. but once it done, its rolling.
Scene issues with missing textures is a user error and I wouldnt recommend anyone to start building their own farm, home or on amazon ( same infrastructure both places ) if missing bitmaps is a problem.
You can build a script that uses Amazon ec2 API that sends your scene from local to cloud in 1 click too.
You can also harnes via VPN: Distributed bucket rendering directly on your screen, however a solid line should be accounted for in this type of setup.
You can make this system for yourself. I have talked to autodesk about selling render power on ec2 via Dev Pay and they TOTALY denied that fits into their EULA.
This makes me question how THIS company pulls their service off as that is essentially exactly the setup I have illustrated for Autodesk. oh and btw, they rip you off too, considering you can hack it together yourself.
I made a concept illustration of the setup and attached it to this post for inspection.