Spend the money and get an Electrical Management System (EMS). While an electrical surge can ruin your day, you will encounter high voltage, low voltage, and Ground issues far more often and those problems can cause a lot of damage. Surge protectors only protect against electrical surges (usually lightening).
Figure on over $300. TRC and Progressive Industries are the main players in this market.
They can be wired into your coach with the advantage of a remote display someplace convenient inside.
Or you can get a portable unit that plugs into the power pole and then you RV power cord plugs into it. One advantage of a portable unit is that you check out power poles without moving the RV when you run into a bad one in a park.