Crystals I believe are very rare, however it will also drop nobs and they are rare, but can seem to get one every unload or 2, obiviously will still take a bit to get enough to use, unless buying speakers!
Last I tested, it was a 0.026% chance to get a random xtal drop. That's roughly 1 xtal in 4000 quests chance.
Don't worry about xtal drops from quests. The drop rate is so low at ~0.026% that you are probably better off going inactive for a few days and returning to claim xtals. Instead farm for nobs which have ~0.95% drop rate and you can use those to regen and purchase stuff. Edit Ata should drop Stacy
I didnt know %, but did realize crystal drops are very rare, just was letting jackie know they would have a little better chance at collecting nobs and by my experience, it seemed to drop one nob every couple unloads. Its not something I would do all the time but if wanting to use for speakers or something like a regen, name change, etc... especially if running ebs with alot of spy only action, it maybe worthwhile.
Quest have always had poor drop rates after the quest has been completed. I can't remember the last time i hit a quest. In the market place there are free offers. But they take some time and sometimes the marketing people need ss of the fact you have completed said offer.
To be honest I think it might be more time efficient walking around on the sidewalk trying to find coins and buying xtals with those than it is doing quests lol.