Their days of growing plants are not behind them but orangeries now a lot more uses, they are used as pleasant sunrooms to relax and enjoy during the day and night.
The Trends In Orangery Designs?

Their days of growing plants are not behind them but orangeries now a lot more uses, they are used as pleasant sunrooms to relax and enjoy during the day and night.
Many people use it as a form of greenhouse, where they can grow plants; which was in fact the original purpose for which orangeries were built and it is also the reason behind the name.
For orangery & conservatory costs, you can check out this 2018 guide.