Those cross class level 20 skills are valuable. As a fledgling crafter/gatherer, you really do want to make use of them.

400 GP for +2 Yield? That's a savings compared to King's Yield 2, which means that you can use it again sooner. You regain 5 GP every 3 seconds, or basically every swing. That's one minute's worth of GP, or 20 swings, sooner that you can use the elemental ability.

If you are actively trying to build up a stash of shards, crystals, or even clusters, and are not able to do the Aetherial Reduction (which does not work for shards anyway) those elemental cross class abilities are your best friends.