Wonderful. I love it when people come up with useful and simple solutions!
My suggestions for you to consider, in order of priority:
1-More destinations. I would use this:
http://brilliantmaps.com/top-100-tourist-destinations/
2-I think it would be a good idea to include another trip cost, for a Saturday to Sunday flight. I'd make that another column rather than a toggle (or a toggleable column!) so we could compare.
3-Some kind of Good Price/Great Price marker. This is difficult though because of the seasonal thing. Maybe below 365 day average is good, and 20% below 365 day average is great?
4-Option to hide destinations!
5-Email alert feature for good/great markers? Probably out of scope
