Dude, you should definitely raise your prices. I would pay at least $19 a month for this. Had to double take when I saw $8 a month.
FWIW there are multiple tiers: $8/mo, $35/mo, $85/mo, $275/mo and I have one custom-priced "enterprise" client.
That's another lesson I learned: The kinds of feedback I get from paying customers vs drive-by trials is completely different and often opposite.
I'd actually like to create a similar sort of service for a different niche, so find this very interesting. I'll definitely sign up and test it out. I'd also love to email back and forth to ask one or two questions about how you came to choosing certain data points over others. Will shoot you one after I sign up.