Radon Test Failed at 4.8 - Would you be concerned if you were the buyer?

The home is new construction, however, has been vacant and closed up for 3 years. Buyers rarely request radon inspections in this area because of the sand soil. EPA Guideline is 4 and below in order to pass inspection.

The inspector mentioned an air exchanger would most likely get the radon level under the desired reading of 4. Most people I've talked with feel the reading is going to be higher because the home has sat vacant for 3+ years. There was also a pipe in the ground which was meant to be used for laundry hook-up in the lower level and had not been capped.

Any opinions or similar situations you may have are appreciated!