It's mostly a Stardock-developed and/or -published bundle and given that, they've done something incredibly cheesy here. While it's generous to give away GalCiv I, it's mostly because, as with the fairly getting-on-in-years GalCiv II, they're not likely to move a lot of units (so to speak) at any price at this point in time. The cheesy thing is that they've included the ancient Trinity version of Sins of a Solar Empire, instead of the more recent Rebellion version which includes everything in the Trinity version, as well as a number of other improvements and new features. Honestly, Rebellion isn't exactly brand-spanking new either, so it wouldn't have killed them to include it instead. (On a slightly separate rant, Stardock literally never puts the soundtrack for this game on sale and $10 is an absurd price to pay.)
Other people have already pointed out the sleazy behavior of the PA: Titans dev, so I won't rehash any of that, but the BTA tier (if you got a ~$5 BTA) is still the cheapest way yet to get this "standalone expansion." Rebel Galaxy, of course, is available for much cheaper due to its previous bundling.
For what it's worth, the other item in the $1 tier, Space Hulk: Ascension, hasn't been cheaper than this, and if you like Warhammer 40K and TBS games, it's well-reviewed. It has 4 $8 DLCs, too, if that sort of thing bothers you.
The $15 tier consists of two TBS games that are relatively new, haven't been previously bundled, and whose lowest price hasn't been lower than $10. OTC is about to get a paid expansion and GalCiv III has a substantial number of expensive DLCs too (many of which are currently on sale at Gamersgate, FYI). Having said the negative things I previously said about Stardock, I will point out here that the company is very good at making turn-based strategy games. GalCiv II was pretty fun in my experience, and the third item in the series is well-reviewed. It also has the thing that I kept wishing Stardock would make for the second game, a single-player campaign.