Thanks for the info! They are doing weekend promotions on the map packs for some time now. I unlocked a couple of them for free and I actually feel bad about it. This game got so many updates (20 or something) over the last 3 years that the devs surely deserve a couple of bucks for keeping this classic TD game alive. I don't buy IAPs too often but this time I will.
Favorites: The Quest Gold + expansions, Mission Europa Collectors Edition, Ascension, Jet Car Stunts 2, Junk Jack X, King of Dragon Pass, Kingturn series, Mecho Wars HD, Mini Dash, Mos Speedrun, Ravenmark, Sonic series, Fall of Angels, Highborn, Solomonís Keep / Boneyard, pixel art games, remakes and ports of classic games.
I started to go back and play the new maps when they started the promotion to give some of them away. It takes me back to the simpler days of Fieldrunners, GeoDefense, and 7 cities. Great fun still, and now I'm feeling guilty for downloading all this goodness for free as well.