A tiered pricing system is when the price of a product or ticket starts low and increases over time or as certain milestones are reached. Lets use buying tickets to a festival or a concert as an example:

Early Bird Tickets (AKA Tier 1): The cheapest tier. These are limited in quantity and reward people who buy early.

Regular Tickets (AKA Tier 2): After the early bird tickets sell out or the deadline passes, tickets move to the next tier, which is slightly more expensive.

Last-Minute Tickets (AKA Tier 3): These are the most expensive, usually closer to the event date. It's for people who waited too long or made a last-minute decision to attend.

Hope this clarifies things!