I can fondly remember the cheap airfares from South Florida to SJO but I think that those days are gone. I have paid as low as $189 round trip but the current prices are in the moon .
I got this ticket from
www.ticotravel.com for a flight on Aug 25 to Sep 5. The same ticket(for a seat on the same plane) was $100 higher on taca.com.
I could not resist the early purchase for the DG Birthday Bash on Aug 28 and the CRT party on Labor day weekend. My guess is that in another month this fare will disappear and the ticket will be well over $500.