www.CostaRicaTicas.com

PURCHASE: By Friday - January 22 (11:59 p.m. Central Time)
DEPART: Saturday - January 23
RETURN: Monday or Tuesday - January 25 or 26

Travel between the United States and non-United States destinations and between non-United States destinations

Quoted fare includes all base fare and surcharges and 7.5% U.S. excise tax, if applicable. Quoted fare does not include the following taxes, fees and charges that may apply to your travel itinerary:
U.S. excise tax of $16.10 for each international arrival and departure in the U.S.

Passenger facility charges (PFCs) of up to $18.00 per round trip
September 11th Security Fee of up to $10 per round trip; one-way travel may incur fees in excess of $5

Each arrival in the U.S. is subject to U.S. inspection fees of up to $17.50. Non-U.S. government ticket taxes, fees and airport charges may add up to $160 per ticket

A $50 fee will be charged for paper tickets issued by Continental. Your ticket will cost $20 more per person if booked by telephone or at a ticket office. These costs may vary by country. To avoid paying this additional expense, book and ticket your reservation on continental.com.

Actually I got the 9am Sat flight with return Tuesday noon.
You have to be very quick, as by 9am on the offer day all the morning flights were booked.
Even better is the 15,000 mile option.

....Even better is the 15,000 mile option.

That depends on how you value your miles, your current elite status, and whether it will make a difference in achieving the next elite level in the current year and whether there are any additional mileage promotions going on. For example. In addition to the 15,000 miles, your opportunity cost includes the 3,104 miles you would acquire for the round trip if you had purchased the ticket. For Gold and Platinum elites, its double the miles for a total loss of 21,208 miles (15,000 + 3,104 + 3,104, it would even be more w/ mileage credit card used to make the purchase). If you value your miles at 1.5 cents (This is a personal value and depends on how you generally use your miles, years ago the consensus was each mile was worth 2 cents, today it generally costs more when purchasing miles and usually costs at least half that amount just to transfer miles you've already earned) that means your opportunity cost is $318.12. So in the above example it would be "better" to buy the ticket. Additionally by buying the tickets elites have the opportunity for one or two free international upgrades to first class.