My first heater core (mid 80's Ford Bronco...I believe) was new from the parts store. The "shove-it" heater core was $10 at the wreckers. (that should be $5 US

)
I took it to the coin carwash, sprayed out the fins, and then blasted it through the tubes, back and forth, until the water was clean running. Worked great, and is ready and able to be used again should I need it.
Hmmm, err, um, scratch all that...
$80 you say? Have I got a deal for you! $40 and you can have mine...that's half price!