The high season for resort prices in the Maldives basically runs from December through April, with December and January being the busiest months because it's when most Europeans want to take a winter break. The rest of the year is considered the “low season” for Maldives resorts, even though the Maldives weather is almost exactly the same the whole year round and therefore there is no best month to go to the Maldives in terms of climate.
Interestingly, July and August tend to be the cheapest months for resorts in the Maldives, so it's quite a popular destination for Europeans who take one of those months off. Better still, many resorts offer drastic discounts during the off-season months, so it's possible to get a water villa at literally half the price you'd pay in the high season.