This question has been answered by absent42. See the first response.
I've used Login and Personalize to only display prices and buy buttons for registered users before: http://modx.com/extras/package/personalize
There are a couple account add-ons for Minishop2, but they're premium add-ons:
https://store.simpledream.ru/packages/users/office.html
https://store.simpledream.ru/packages/ecommerce/msprofile.html