Cast a random Lesson spell without paying its mana color. If that spell has X in its mana cost, X is 3. (As of today, there are 20 lessons. Perhaps look up a list and roll a d20?)
NM-Mint - $8.20
Lightly Played - $7.40
Moderately Played - $6.50
Heavily Played - $5.70
Damaged - $4.10
NM-Mint Non English - $8.20
Lightly Played Non English - $7.40
Moderately Played Non English - $6.50
Heavily Played Non English - $5.70
Damaged Non English - $4.10