The Catholic church is always the most opulent one in town. And one always reads about how priests take a vow of poverty.
I was not brought up Catholic, so I don't understand that. I was brought up in the Presbyterian church, and the local Presbyterian church is one that allows us to use their building for recitals. Pretty good acoustics, and the organ pipes make a nice backdrop.
The reason for the beauty of a Catholic church is to glorify God with the very best man has to offer. A Catholic church is not a recital hall, it is a house of prayer and worship. Sacred music concerts may be done because they glorify Our Lord. Different churches have different thoughts on the matter.
Priests in Orders take a vow of poverty and live in community on very little. Priests who function in the world in a parish have a salary from which they pay taxes, health care, car payment, car insurance, etc.
Compare an urban Catholic church in the South -- usually almost falling apart -- to a suburban evangelical megachurch -- as much opulent shopping mall and music venue as church, and you'll play a different tune.