Just replaced the batteries on the backup rigs last year, about $150 each rig; but I get bigger batteries than required and they usually last me 4-5 years. Plugs, wires & distributor on the plow truck was a whopping $35 total. It'll be around $50 when I do the other backup rig this spring. Primary rig has no plugs, wires or coils (diesel w/ grid heater).
If I look at the registration costs, I spend $200 every two years to register 3 rigs. Not too bad actually, since its $100 / rig / 2 years. Yes, the math doesn't work out, but one rig has amateur radio plates, so the registration renewal is zero.
My ol' '89 ranger was a pain to change the plugs since you had to pull the throttle body to get to 3 of them. It was a 4 cylinder with dual coil packs and 2 plugs per cylinder. I took it in everytime I had to get the plugs changed on it because it required a computer reset while you were pulling things apart. Real pain in the kiester!