Sometimes, changing items in the pricebook or uploading a new pricesheet can result in your pricebook line items being set to $0.00. Do not panic! To fix this, the task picker needs to be reset.
The easiest way to do this is to change your Finance Markup, wait for the Finance Markup to calculate, and change it back! This will force the pricebook to recalculate the prices, resulting in pricing going back to how it was before.
To change your Finance Markup, navigate to Company --> Settings. Under the Pricing/ Finance section, change the Finance Markup. This can be adjusted by .01% and the pricebook will recalculate its prices. The system will notify you when the calculations are finished. When you receive that notification, you can change the Finance Markup back to where it was before!