It all depends where you originate from xxx-SIN-MLE on SQ should not be that much more than xxx-SIN but since you did not say where xxx is. Doing a separate SIN-MLE will be expensive if you want a non-stop. Flight times on SQ ex-SIN / ex-MLE are not particularly convenient either - adding cost for additional nights / day use rooms in MLE.

As others said - the Maldives are very expensive - everything is in USD but these days that is a bit of a help depending on your home currency.