In this promotion, Google's answer to that question is that at the very least, you can be sure you're not selling to a patent troll. They may end up using your patent, or they may not, but they are promising that they will not use the slimy tactics associated with patent trolls.
But the thing about patent trolls is that they're looking for a very specific type of patent: an overly broad one that probably should not have been issued in the first place.
If you don't have that kind of patent, but you do have a patent that is clearly valuable otherwise, then the pool of potential buyers probably won't include patent trolls, so the purported benefit of selling to Google (avoiding selling to patent trolls) is moot.
In which case, you might end up getting a good price from Google (the price you yourself set), or you might end up getting a better price from some other buyer.
But the nice thing about this promotion is that, assuming you're confident there are other buyers out there, you can set your price a little bit higher than you think it's worth and see if Google is willing to bite. If not, go sell it elsewhere.