The thing you have to remember about space, is that even if you specify it at the Database level, it is given at the AMP level.
When a DB has XX GB of MaxPerm, in fact it's each AMP who have a (XX / NbAMP) of MaxPerm.
So yes, skewed tables have the downside of wasting space.
You should change the PI of your skewed tables if possible.
You can even try NO PRIMARY INDEX (NoPI) tables, it will be evently distributed, but of course you will have impacts on queries, so this is not something to do blindly.
To add one other thought to the good answer from @Waldar ...
A NOPI table will typically be evenly distributed if you load it with data from outside of the dbms platform (using tpt stream, load or single row inserts etc.)
But, if you load it using an insert/select then the data distribution of the NOPI table is determined by the data distribution of the final Spool file - which you have no direct control over. If this becomes a problem then use the 'hash by' clause on the insert/select.