Starting in late September through the middle of December daily flights are available at the listed price on this route. There is no minimum stay required and checked baggage is included, which makes this deal much better than what other airlines are offering. There are a few blackout dates around Thanksgiving but other than that this fare is wide open and easily booked on the Copa website.
As an example below, I found tickets departing BOS on Friday, November 9 and returning from SJO on November 17, 2018.
Need a room in San Jose? Here's what we found for the listed dates on Hotelwatchdog.