Those readings are very high, and if you're sure they are correct you are warranted in your haste to fix this problem
It's a couple grand for the simple mitigation (drill hole through basement slab and install PVC pipe with fan to depressurize below the slab and exhaust air/radon somewhere above the roofline (well away from any ventilation intakes). If you've got a sump, make sure they seal it up. Often they will use the sump as the "pickup point" for the radon mitigation system, which is fine.
Things get more expensive if you have a home that doesn't have an intact gravel bed under the slab (some older homes never did, and some have beds that have silted up over the years). In this case, a simple pipe won't successfully depressurize the entire underslab area and a more expensive fix will be needed (e.g. installation of a manifold of perforated pipe under the slab, with al the digging that entails).
Sealing the walls and sealing the cracks is claimed by some people to lower radon readings, but I don't have a lot of faith that those results will be permanent (new cracks from settling, esp in the corner between the slab and the wall). Plus, while they might bring your readings down some, I doubt these measures would get you below the "action level" of 4 picocuries/liter.
If this were my house, until i got this problem fixed I'd close any doors leading down to the basement, close any HVAC registers or intake vents you've got down there, and open windows on opposite sides of the basement to dilute that stuff. I wouldn't be afraid to go down there to do laundry etc, but neither would I do my aerobic workouts in the basement.
Are you on a well? If so, given the high radon readings in your neighborhood, you should definitely test your water for radon. Lots of radon can be released into your home via the water when you shower or wash clothes.