We can compare prices all day but just because someone went for X and we think Neil is better doesn’t mean we’ll get more money.
Worse players will be sold for more and better players will be sold for less it’s the nature of the beast. Comparing him to Henderson, who captained both England and the best Liverpool in decades plus arguably one of the best PL sides to ever compete, is probably a stretch imo similar type of player but he’s not on that level. Henderson had 4 seasons of PL football under his belt at Neil’s age.
Being a HGN player will definitely add some value if it’s a PL club.
Hindsight is a great thing, I remember before Henderson left a lot of fans were critical of him saying he was a liability defensively and only useful out wide etc.and Newcaslle got twice as much for Carrol at the same time which I suppose proves your point , but we don't have to sell and that is crucial . I would not consider anything less than 30m for Dan and I hope all concerned wont be either. Thanks to the present owners we are no longer the mugs we were in the transfer market , just the opposite in fact and long may it continue.