If easyJet prices drop after you've purchased them there is a "price promise" whereby they will refund the difference with a voucher against future flights
Article 26 Price Promise
26.1 If You have, or the Booker on Your behalf has, made a Booking directly through the Website and You, or the Booker, subsequently find that lower fares (when taken together with all applicable fees and charges) for the same easyJet Flight have become available, You will be refunded the difference as a credit voucher against future Flights on easyJet. The only exception to this “price promise” is if the lower fares have been offered as part of a promotional offer that is launched after You have purchased the Flight. For the avoidance of doubt, this Article 26 will not apply to any Booking made on Your behalf by any licensed third party booking systems (e.g.: travel agents, screen scrapers) or through easyJet’s Call Centre.