This looks like an interesting product; I didn’t even know this level of gmail plugin was supported by gmail.
Help desk ticketing, with assignment, priorities, notes, and built-in response-time metrics, all within your gmail inbox (support emails are in a separate tab from your regular email).
The cost is $49/month for the ‘unlimited’ plan (capped at 5 users for $29/month).
I think this product could be a good fit for libraries dealing with patron reference/help questions, I think many libraries don’t have very user-friendly interfaces for this at present. I think the price is pretty reasonable at $1000/year, probably cheaper than most alternatives and within the budgets of many libraries.