While Ryanair regularly offers very low fares from Malta to Sicily (Trapani), it’s worth pointing out that it currently has a number of one way fares from Malta to Trapani available at just €19.99, with this price extending into May and June. Where the €19.99 cheap flights to Sicily are not offered, there’s also a number available at €23.99.
Bear in mind this is, of course, the new, “nice”, Ryanair.
For comparison purposes, a return in May or June on Virtu Ferries (to Pozzallo) will cost you €84. Air Malta flights (to Catania) vary substantially depending on exact dates, but average out at around €100 return.