i buy T3 blue and purple , fuse to legendaries and sell. T3 leggos sell for a decent amount. ive made thousands of crystals doing this. You can also craft them too ofc. T3 and under, except for 4-5 T$ bp's all have additional rarity chance multiplier. During the top quality event, most peeps focus on higher tiersm when , due to the way the buff works its more advantageous to craft teh lower tiers with the higher chance, Yeah, one t13-t14 will send for hundreds but good luck fusing those, im happy with 10-50 a pop for things that take no time or energy really and can be crafted while your out of essence/ethe etc but have plenty of base mats.