Since the start of the NBA season, Luka Doncic’s performance in the sports card market has been somewhat uneven, with record-setting high-end sales coinciding with a softening in raw 2018-19 Prizm and Optic RC values. However, the Mavericks’ improved play of late has nudged Doncic back into the MVP picture and boosted prices for several of his rookie-year cards. Consider the following three 2018-19 issues: 1. 2018-19 Donruss The Rookies #3 Luka Doncic ($30-$80) Sitting for some time in the $20-$50 range, Doncic’s “The Rookies” has almost doubled in price, not a bad increase for an insert from a lower…