I think state governments go after large purchases, like (pricy) wedding rings, aircraft, cars, or anything like that simply because that's where they'll get the biggest return.

It might be an urban legend now, but I've heard of a soon-to-be-married couple purchasing a wedding ring in Portland, OR, and making several trips from SF to Portland. They took photos of the ring at typical Portland attractions (Mt. Hood, Multnomah Falls, food carts), and did that for several months. Doing that, after adding up all the flight/hotel tickets, was still cheaper than buying the ring straight up in California.