What is the weather like? Prices are very low in Costa Rica during monsoon season, but you'll be in a monsoon.
Is the resort under construction or is this deal for the "old" section?
For flights, check the connections and layovers. Are you willing to have 2 connections and a long layover to save money?
What are the dates of travel? Most people want to travel over a weekend so Monday - Friday trips can be available at a discount.
Is everything open? Alaska cruise tours have reduced pricing in May because areas of Denali National Park aren't open yet and some excursions may not be available.
Sometimes you just luck into a great deal. As a travel agent, I can help you navigate the different options and find the best value and the best vacation experience for your price range.