The honest answer is between $60 and $500 a day, and the range is that wide because "PA system" means very different things to different people. Here is what the components actually cost, so you can build a realistic number before you ring anyone.
A pair of 12 inch powered speakers on stands covers a backyard or a small hall for up to about 60 people. Add a cabled microphone at $20 for speeches. You will not need a mixer if you are playing from a phone.
Two 15 inch powered speakers, a subwoofer, and a wireless microphone so the best man is not tethered to a stand. The subwoofer is what people notice: without it the dance floor sounds thin no matter how loud you go.
Two tops, two subs, a mixing desk, monitors so the band can hear themselves, and enough microphones and stands. At this size, ask about delivery and set up. A band arriving to a room where nothing is patched is how a night runs an hour late.
Speaker stands, cabling, power distribution, and a spare microphone. Also the hire period: our day rate is 24 hours, with each additional day at half price — so a Friday to Monday hire is charged as two days, not three.
