My good friend Dr. Google says the carriages are 15JOD one way, 25 round trip, tips additional. I suspect they're customary, but I don't know how ticked off people get if you don't tip. (You didn't ask, but one Jordanian dinar is about US$1.40 these days.)

However, other sites say the carriages are being phased out and replaced by electric golf carts. I assume the fare is comparable, but I didn't see a number.