When my parents lived in AZ, their car registration fees/taxes were also quite high. I guess that's just Arizona's way of getting its pound of flesh from you. Sorry about that.
We just titled & registered a new TT we bought in Utah. Interesting - Utah collected no sales tax, so we had to pay it in Idaho (same rate, so it didn't matter). Added to our relatively high annual RV tax, it made for quite a bill! Fortunately we won't have to pay the sales tax more than once!
Idaho is much more expensive, due to that annual RV tax, to register campers in than Illinois was. Such is life.