I currently evaluating several hosted hotspot solutions.
Each one has it's advantages and disadvantages, which I won't go into here.
As for pricing structure, they generally have either a set price/month/site or price/ticket or some sort of combination.
I have several hotspot already, using a "hotspot in box" (Zyxel G-4100) solution. Some are profitable, and others are very quiet.
The sort of solution I'm looking for is one where I pay per ticket, upto a monthly limit, per site. This accommodates the low usage sites and limits expenses on the high volume sites. Also a flat price per ticket would be advantage. One of the above services a three day ticket is more expensive then a 1 week tick
I use pre-paid tickets, and another shortfall of the pay per ticket solution, is that I would need to supply 50-60 pre-printed tickets to a new location, which I may not see any returns for several months. If I could pay as the ticket are used, rather than when they are generated.
This is just a couple of ideas for you. Everyone has different needs and I don't believe there is one "perfect pricing structure", just the "perfect pricing structure" for me.
Cheers
Dog