Edison has 3 zip codes, 08820, 08817 and 08837. If you drive around, you will see many big houses in 08820, so the price is high for bigger house, whereas 08817 and 08837 have many smaller houses, like 3br ranches, condo/townhouses, so price seems to be lower, and it make sense for smaller houses to list lower, right?
If you come to Somerset, you will see even cheaper price. Like in our Forest Gate townhouse, you can get one for only $250k. But then, when I went to Philly work, I had to drive to Edison Train Station first to park the car there then take train to Trenton, it is a bit inconvenience. But, if, say, you work at Rutgers or Johnson and Johnson, Somerset is as convenient.