Doesn't need to be.
Let's have a look at all Championship players with 10 or more goals in the 25 matches of the Championship (so a similar ratio as Wood has managed in the PL, other than this year):
Mitrovic - Fulhams best player by a mile, in a team that want to go up, cost Fulham Ł22m - no way they are letting him go for less than 30m. Played for Newcastle previouslly and was a flop.
Brereton - Newcastle will be battling the likes of Sevilla to get his signature, and blackburn value him at more than 20m, but might accept 20m given he only has a year left in his contract. The issue is that he might prefer Sevilla, and it could easily cause a bidding war pushing his value to closer to 30m. This is also his first season where he has shown any aptitude for scoring goals - the previous he scored just 7 in the championship.
Solanke - cost Bournmouth 19m, no way they'd accept in jan a fee of less than 30m given he has done better in the championship
Weimann - is 30 (so same problems as Wood re: Age) has played in the PL before without scoring many (17 goals in 113 games) but has definitely done better with 12 in 25 this season in the Championship (but ONLY this season - before this season in the Championship its 9 in 81 for derby, and 21 in 92 for Bristol City). Very cheap, but given his previous inability to find the net, and age, I can't see this being a better transfer than Wood, not even close
Piroe - never a goal scorer back home in the Netherlands, he has 11 in 21 this season. But again, thats half a season - no clue about whether he'd be able to step up to the PL, so very risky signing given the scenario they are in.
Grabban - 34, so would be cheap but is 4 years older than Wood, had played 24 games in the PL before (for 1 goal return). Doesn't really score that many in the Championship - in 135 games for Notts Forest has scored 52 goals (so a worse ratio than Wood has in the PL the last 4 years), and this year has got 10 goals, but in 23 games.
So out of those players who you could argue have scored enough this year in the Championship, which do you think NEwcastle should take, and for how much?