Solder has been overrated on this board from the first day he arrived. That doesn't mean that 100% of the people on the board overrate him. It's just the general position of the board.
You note the real key, which is positional value. LT is sort of like QB in that sense. Solder is an above average kind of LT who really needs a top end LG in order to maximize his game, because it allows him to sort of overcommit against quality pass rushers. He's not a top 3-4 player on the team, though, regardless of his money. I'd put the following positional players above him, without even getting to anyone I'd consider a close call, or the 2 STers I'd also consider no brainers (Gost, Slater):
Edelman
Brady
Gronk
Collins
Hightower
McCourty
Butler
I think a Matt Light v. Nate Solder poll would be very interesting...