The Celewave 0185417U05 Is A Good Quality Duplexer, & The Price Is Reasonable. They Can Go For As High As $1150 To $1250, But I Would Pay $500 To $600 For A Good 4 Cavity Used Duplexer With Similar Specs.
The 250 Watt Rating Is Less Relevant For GMRS Use, But More Important Is The Isolation & Insertion Loss Specs Of The Duplexer. If You Want A Commercial Grade, Good Quality Duplexer, This Is A Great Choice.
It Will Need To Be Tuned By Someone With A Service Monitor, As It Or Any Duplexer Is Specifically Tuned For A Single Pair Of Repeater Frequencies.
A Duplexer Is One Of The Main Components Of Your Station - Don't Skimp Just For $$ If You Can Afford It.