I checked SWF-EDI (their first daily flight) for the first few weeks and one way fares are available in all tiers of coach (low fare/low fare+/flex). They were as low on some days as $109, but averaging $200-$600. Only one day were they totally sold out - June 16, their 2nd day of service.
Only 2 flights are running daily all summer (EDI and DUB), with the others 3x/week. In the Fall, they all reduce back to a 3 days per week.