My analysis was strictly based on Rares/Mythics. Both Demonic Tutor and Mishra’s Bauble are Uncommons in the set…there are actually a fair number of Commons and Uncommons worth more than $5 in the set (in fact I count 12). Normally, I don’t focus on commons or uncommons unless they are 4 of eternal playable and not reprints, however, you have a fair point that thanks to the large set size of Mystery Boosters the uncommons are likely close to a standard set rare and the commons are likely more like a standard set uncommon.