And all presidents do this. I think they should pay for non-official travel. GWB was low key, hiding out in Crawford but it took a lot of $$$ to secure that place.
Not really. A good security system (one time fixed cost), and maybe 3-5 Secret Service agents when he's not there. Call it $100-200k one time cost, maybe another $100k for vehicle(s)/weapons/misc already on the books and $150k-$300k in annual expenses. Sounds expensive, but honestly, a single POTUS mobile visit is probably five times that expense, per day. During a POTUS visit, sure, it'd hop up quite a bit.
Fixed site security is cheap compared to the prep work of a First Family visit. I saw the First Family visit the Baltimore Aquarium, probably 50+ local cops (all in vehicles), over a dozen feds in fed vans and a couple Suburbans. Local businesses in Inner Harbor were essentially shut down with no notice for over 4 hours, and the revenue losses alone were probably higher than a fixed site security annual budget.
Those kinds of unannounced visits can be highly disruptive to the locals. Not a huge deal, except it's not even taken into account with a POTUS or First Family visit.