As many are doing, the trick is to find alternate routings that don't attract the attention of the revenue managers at the airline. For info, what happens in these circumstances is not a price increase as such; what you have are numerous booking classes on the flight, correlating to different price bands. When there's a draw like this, what they do is close out the cheaper classes so only the higher prices are available. It amounts to the same thing from the customer perspective of course. The revenue managers will update the flights within minutes, so it's extremely difficult to be sufficiently quick off the mark to book - best bet is to have a selection of bookings almost completed and ready to hit confirm as the draw happens. Even then you might not be quick enough. The key to getting something cheaper is looking at the point of origin into Barcelona on the final sector. If it's not from somewhere that is in high demand, then it won't be much. You just have to get to that midpoint. My advice would be to look at all the flights that operate out of Barcelona, and look at how much it will cost to get to that destination, then fly from there.
As for the day trip, the reason that's so expensive is fairly easy to explain. Aircraft are chartered on a mix of demand, flying time, and overall chartering time to come up with a final figure. That aircraft is going to be on the ground for quite some time, when it could be doing something that earns revenue. It's not just a question of how much it costs to park it at the airport, it's also a matter of the lost potential revenue of it doing nothing built into the quote. Parked aircraft are massively expensive ornaments. If the aeroplane landed at Barcelona, and did another rotation straightaway, the seat cost would be somewhere around half what is being charged - it's that gap in time that makes it so expensive.
One other thing that's been alluded to in terms of routes, have a look at flights into Girona and Reus, both of which are relatively close to Barcelona - again via a European midpoint I'm afraid.
Hope that's of some use to someone.
