Checkout Bestbuy. They have been selling the iPad mini 4 16GB wifi+cell for $280. It goes in and out of stock but I was able to snag the gold one last Saturday.
Contacted AT and T about Tethering to phone vs Cellular Activation. Add a new device to my current 3Gig wireless plan, $10/mo. To use my phone for tethering, I must change data plan to 6Gigs, which is a lot more than $10/mo