The price of an event promotion with our service is based upon the price level for the category of the event. If you started your post with just one category and then added more, that may explain why the price changed. Our system will pick the price based on the highest level of category selected.
For example: if you selected a "Kids / Family" category then the price would be set for the "Lifestyle" price (see all pricing levels here). If you then add the category to your event "Festivals", the price would be bumped up one level to the "Entertainment" price.
Before you purchase your promotion with our service, you are able to edit your event and change the category. After saving your event with the new category, you will then be able to upgrade at the price associated with that category.
In the image above, the initial category was a "Local / Community" category, which is the lowest priced option. The price I would have seen at checkout was less than $50. However, when adding my full event details, I added the "Dance" category, which moved my price to the higher "Entertainment Plan" price of $99. If I keep the "Dance" sub-category, then my promotion goes to more sites that are relevant to entertainment events. If I edit the event to remove the Dance sub-category and keep the Local / Community category, then the price is lower and the number of sites will be less.