Morg shop bugged.
This has happened not just to me but others too, it seems. Morg when playing support it seems the shop items wont allow you to buy or it wont correct the right price.. Ex. Zhonya last cost is 300g to upgrade, but when trying to purchase the item it reverts to the original price. The item does not allow you to purchase it.
Only way ive seen to resolve this in game so far is to disconnect and reconnect mid game.
But, only champion I'm having this problem on or seeing others have this problem is morg, specifically. When I faced one they had the exact same problem
, I think it may be an issue due to the support item quest, as it only happens as far as i notice when i have completed the quest