It's very interesting that this device which seems critically necessary or your risk complete and catastrophic failure is 1) produced by only a very few manufacturers and 2) does not come with most units sold as standard equipment.
I'm not questioning their ability to control power safety, I'm wondering why, if they are so necessary, are they so little used and never provided as part of OEM equipment.
We see purchase threads in here where everyone is encouraging new buyers to negotiate for added extended warranties, power tongue lifts, free canopies, better batteries, and any number of other add-ons but I've never seen one of these threads suggest to negotiate a free power manager/surge protector as part of the sales agreement.
The people who spend the $200-500 to purchase one are naturally very passionate about their benefits as an insurance device, you have to be with that sort of financial investment. People that don't have one, like me, still wonder why this isn't already included if it's as essential as brakes, wheels and tires. Or available at a far far far more reasonable expense than an average of $300.