If you wanted to make this post about Gary Payton perhaps then perhaps you shouldnt have titled the post "A solid way to identify Marcus Smart's current value...", because looking at where Payton II gets picked is a terrible way to gauge Marcus Smarts value.
Wait, but why is it a terrible way to guage Marcus Smart's trade value? Value is all about scarcity. The supply of NBA point guards with NBA ready defense, strong rebounding, and below average handling/passing/scoring abilities is about to go up. Gary Payton II's draft position will tell us a lot about where other NBA teams value that skill-set.
And more importantly - if you're an NBA GM trying to acquire a defensive point guard, are you going to give the Celtics anything above the value of Gary Payton II's projected draft position when you KNOW you could draft him and get similar production? If so, how much more are you willing to give them? Would you trade a lottery pick for Smart while Gary Payton II is on the board? Would you trade pick 16 for Smart if you knew you could pickup Payton at 24?
Just to be clear here are Smart's NBA numbers via nba.com
GP MIN PTS FG% 2% 3% FTA FT% TRB AST STL BLK TO
Year 1 67/ 27.0/7.8 /36.7 /.410/33.5/ 1.9 /64.6/ 3.3 /3.1 /1.5 / 0.3/ 1.3
Year 2 61/ 27.3/9.1/ 34.8 /.427/25.3/ 2.7 /77.7/ 4.2 /3.0/ 1.5/ 0.3/ 1.3
Smart's draft position (#6 overall in his draft) was based largely on the assumption that his best offensive attribute in college - his ability to get to the rim and score or draw fouls - would translate to the NBA. So far it hasn't. While his volume did increase this year his efficiency actually dropped slightly. He did sport better than a 2:1 A/To ratio both years and obviously his steals and rebounding numbers are very solid. Intangibles also play a big part in his value, effort, determination, leadership, and work ethic are all valuable traits, but how MUCH value do teams place on them? Remember, Draymond Green wasn't drafted until the second round.
My take is, given 27 minutes a night Gary Payton II could replicate Smart's on court production while providing similar versatility as a defender. Some people feel because Payton II is a year and three months older than Smart the difference in their potential is drastic. This assumption seems tenuous to me, but only time will tell.