A 9th level casting of the spell could create up to about 112.5gp if we go with the 3.5e economy(which doesn't have this spell, anyways), or only just over 1gp going off the 5e economy(it takes about 4 gallons of seawater per lb of salt, and you can purify 90 gallons casting at 9th level).

It's really not that good. Sure if you're level 20 and use all of your spell slots on it it's a decent sum of gold... but you're also level 20. Go rob a bank or something.