If the price goes up after you have purchased your ticket, consider that you made a good operation!
However, if the price of a ticket for your exact itinerary goes down after you have made your purchase, you may receive compensation. (Always the famous MAY)
If the price change is over $25, the airline will usually issue a Miscellaneous Charges Order for the difference (MCO), if requested - if you don't ask, you don't get it.
There are fees associated with the issuing of a MCO. This voucher is good toward future travel with the airline. It's always free to ask!