$7.50 or $8 per person on any of the airport shuttles (Strip price...may be a dollar or so more to Downtown).
Flat rate, so no worry about a price gouge. Same rate on all the shuttles.
Tip the driver a few bucks.
I'm guessing that at 5pm, probably will be a long taxi line. They keep it moving, but it can be really long with you winding through the ropes like a lab rat, dragging your luggage. And then you can't be sure how much you'll be charged. 5pm traffic will drive the cost higher.
That's why we like the airport shuttles. One price no matter how long it takes.