Funny, I did the same thing recently (Esco to SAN, and back again) to determine approximate pricing and noticed the same thing, just figured it was the holiday effect.

That being said, try flipping to another app (I don't think the app can tell what the "other app" is, at least on Android, but I'm also signed up with Lyft as I pit them against each other) and flip back a few times, waiting 30 seconds or so between apps. You'll notice that frequently, the price will continue to go down somewhat (sometimes quite a bit) with each flip, 'till it finally "settles in".