I think a big part of being good at this is being an early adopter on guys that absolutely look the part and being willing to “buy high” compared to their months-old rookie draft value, before we actually get close to the real high point. Now you can certainly whiff doing this, but you can also lock down guys before they go from risers for some to studs for all.
It doesn’t even just apply to rookies. Last year I got Waller for free all over but sold in one league for some prospects, thinking that I’d done well just to capitalize on the announcement that he’d be the starter. After one actual NFL game or so I immediately bought him back and made the guy feel like he’d made a quick profit (which in some ways he had although I preferred my pieces) on my indecisiveness about Waller—but imo it was actually decisiveness and realizing I’d erred in thinking I’d already “sold high” when he clearly had a lot of height left in him, value wise.
This has been the foundation of my dynasty strategy for the last 3+ years now. It seems like every year I'm getting in a discussion with someone on here who is saying "don't overreact to 4-5 weeks" and I'm replying with "underreacting to these 4-5 weeks is even more detrimental". Glad to see someone coming in on the same side this year.
Like you said, it doesn't apply only to rookies. Dynasty rankings change wildly from year to year but people/rankers are tentative about making big moves in-season, instead saving them for the following offseason even though the likely path is pretty clear in-season.
While I realize startup ADP isn't a perfect reflection of trade value it is probably the closest thing we have to putting a historic number to it. Look at some of the guys that made moves in startup ADP from 2019 pre-season to 2019 4-5 weeks into the season and how that trend continued and amplified into the following offseason.
David Johnson fell from late 1st startup value to late 2nd startup value 4-5 weeks into last season.
Le"veon Bell fell from late 1st startup to early 2nd startup.
Odell Beckham early 1st -> late 1st
James Conner early 2nd -> mid 3rd
And the same thing in the other direction
Derrick Henry mid 4th startup pre-season to mid-3rd in October
AJ Brown mid 8th -> early 5th
DK Metcalf late 7th -> early 5th
Chris Godwin mid 5th -> late 2nd
Obviously it's not perfect and there are guys like Mixon who bounce back. But consider that at this time last year selling OBJ for 1st round startup value was "selling low". Selling Le'Veon/DJ for 2nd round startup value was "selling low". Buying Derrick Henry at 3rd round startup value or AJB/DK at 5th round value were all "buying high". Then consider what all those guys were worth once the offseason rolled around even though their pace through the rest of the season didn't really change.
There are plenty of guys that will follow that same trend this year, even if they seem obvious. "Overpaying" for Claypool or Lamb or those guys is fine by me because buying high now might be the cheapest they will ever be moving forward. Even obvious ones like Metcalf. I look around trade threads and I see people wary about trading away Michael Thomas for DK+. Yet it seems fairly likely/predictable that next offseason MT will not be enough for DK and even something like MT+1st probably won't be enough. So he's a guy I'm buying "high" everywhere I can even at "outrageous" value because I don't think we've even begun to see "outrageous".