let's say you spend $100 on (4) "average brand" CVDs. They last 6 months. Then you buy another full set because you still don't want to spend the money on UE stuff. They last another 6 months.
You would get 1 years worth of use for $200.

OR

Buy UE units for $180 and they will prolly last a few years, and it's a beefier set-up so they may last forever.