Arkansas has special categories for 1/2, 3/4, and 1 ton pickups and vans separate from passenger cars and motorhomes.
My F250 falls under the 3/4 ton class so it's $23.89 with decal fee and postage.
For some odd reason, my motorhome falls under the 3,001-4,500lbs class despite being a 1 ton van chassis, and weighing far more. Technically it should be under either the 1 ton truck/van class, or the 4,501lbs and above weight class. So, it's $27.89 with decal+postage. I'm guessing they are going by the stripped cutaway chassis weight before the RV was built onto it. Eh it's only $4 difference annually.
EDIT: Oh, I should also mention that Arkansas has separate personal property tax on vehicles based on the estimated valuation of it's age, make, model, etc. So, that's more or less a version of registration fees, though you owe it even if you aren't driving it, unlike actual reg fees. So tack on another $20-25 each in annual tax for each my IDIs, and another $10-15'ish for my cargo trailer, which has permanent registration.
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