For a tiny church, so naturally a lot of emphasis on cheapest price.
Currently they are using a Shure PGX24/SM58 which a search of GC shows is about a $400 system.
There aren't any open inputs on their mixer, so four single systems would require adding another small mixer in the chain.
It doesn't appear to me that Shure or Sennheiser has an affordable four channel system. (If they do please point it out for me.)
They want three handheld mics & one headset.
$400 - Nady U-41 Quad Handheld Wireless System
$95 - Shure PG1 Wireless Bodypack Transmitter K7
$39 - Shure PG30TQG Cardioid Condenser Headset Mic
total = $534