If you need to offer free or comped tickets, or import tickets, then the Advanced, Professional, or Plus Plan is required. If all of your tickets are paid, and you don’t need the extra tools that the paid plans include, then the On Demand plan is a good fit - you will only be charged when you sell tickets ($1 per ticket).
Independent of features, it makes simple financial sense to be on the following plan, based on how many tickets you sell in a month:
Sell 0-50 tickets per month: On Demand (or Advanced if you want the extra features)
Sell 51-400 tickets per month: Advanced
Sell 401-4,000 tickets per month: Professional
Sell 4,000+ tickets per month: Plus+