I used a cheap 10-port USB hub for a while that cost me around $12. These days, I have a syncing cart that holds up to 32 iPads that costed significantly more. I can’t say that the cart is much better than the USB hub was.
Just make sure that the hub is powered—or you won’t be able to connect more than one or two iPads. Also, I don’t know if your iPads will fit with their cases on, but you should consider getting a dish drying rack to hold them while you are syncing them.