My girlfriend and I are currently living in different countries, and meet occasionally for a few days every month or so. We don't really care all that much where we are going, as long as we don't need a visa (we're both in EU), just so we are at the same place and time for a couple of days.
I'm flying from airport AAA, she's flying from airport BBB, we need to find an airport XXX (not a euphemism!) which is cheapest to fly to overall.
Bonus task: Flights are first and foremost, and we could live with a somewhat more expensive accommodation as long as we can get in and out easily. Since the accommodation cost is comparable to flight cost for such a short stay, we'd like to have some sort of rough idea what we're going to pay for a certain type of accommodation, for example three-star hotel.