My parents had a house built in 2001 when I was living at home. The radon level in the basement was several times above the EPA action level.
The house was built with a "passive radon mitigation system" which was essentially a sealed sump pit with a 4" PVC vent pipe leading to the roof. There was a perimeter drain field attached to the sump pit as well.
I added an inline blower to the vent pipe and a manometer to monitor the sub-slab vacuum level. Subsequent re-tests showed radon levels *well* under the EPA limit. Total cost was $200 or so.
The blower has been running 24/7 for 11+ years now.