A lot of the events we work with will use a tiered system for their tickets. This might look something like:
Early Bird
General Admission
Final Release
...or a variant of that theme. These tickets are functionally identical in every way except the price — the second tier (General Admission, in this case) is priced higher than the previous one, the third (Final Release) again higher than the second etc... and in most cases only become available once the previous tier's allocation is completely sold.
The thinking is that would-be attendees are incentivized to commit to an event sooner rather than later by being offered a ticket at the lowest possible price. It also gives a sense of how popular the event is, as over time the sales move through the tiers and people get an idea of how close the event is to completely sold-out (and therefore making sure they get one in time), without ever having a number figure shown to them.
Another potential difference in ticket price might be due to additional offers/perks, and as such might be named 'Premium', 'Gold', 'VIP' or other such things. You'll find more info about those ticket types on the event page itself.