I have been using Camco $10~$12 regulators for more than 25 years and never had one fail (have left a few at CG's by mistake). I do presently have a failed $75 Watt's regulator for my house.
The RV specific regs. marked "high flow" provide enough water for any type of use. I used to keep a gauge on it to monitor pressure but it was always spot on (40psi) so I quit using it.
There's no need to spend a fortune on a regulator.
Also, the PEX lines don't have any issues with much higher pressure but the faucets and toilets do. A reg. is a must for those if pressure is high.