This is such a great idea. Well done. Someone I know someone in real estate that did this for a big festival in my hometown. They said it generated around the same amount of impressions for a similar price.

I would argue that because it costs practically nothing to publish branded geofilters, if you cannot really measure ROI, who cares? I would take 214,000 views for $15 any day. This is way cheaper than Facebook per impression and even though it may be less targeted:

1. Snapchat takes up the whole screen (no distractions)
2. People view snaps mostly from those they know, trust or like. Therefore, even though a Snapchat geofilter impression is less targeted, it builds trust better than a Facebook impression.