Churches that spend a lot on singers make me sick. That's why I quit my old choir.
It depends on what kind of singers they are spending money on. If the singers can sight-read and sing with clarity and precision all the time, and come to every rehearsal and service, they are worth the investment. I'd make the same argument in favor of investing in a top quality pipe organ or a church with good acoustics. If you build it, they will come. If you put forward mediocre music, you will have mediocre worship.