I've looked in all of the topics here regarding Maker, and I have not seen anyone post about this, so I thought I would.
You have the ability to upgrade your LQ (Low Quality) gems into MQ or HQ gems.
Maker has three distinct groups for upgrading and appraising: STR/DEX/LUK/WIS crystals, Black/Dark Crystals, and everything else. The probabilities and costs for each group differ slightly. It'd be wise to put these in your calculations when deciding what to appraise or upgrade. Please view the following tables to see these differences.