That assumes that better finishing is the only reason haaland scores more goals, his movement and pace get him into positions where his xG might be high but another striker wouldn't, there's more aspects in a player being a great goalscorer than just finishing.
Well mbappe is the second most expensive player ever and he's a goalscorer, when Ronaldo went for 80m, in terms of the way fees have inflated that would have exceed neymar if it was today. The biggest issue of course is that teams simply don't sell the top goalscorers at their peak. Suarez went for 80m before fees went totally crazy too, kane was talked about as 160m at his peak, what would a peak lewandowski have sold for, what will haaland sell for? Goalscorers are so valuable, teams rarely sell them, they either run their contracts down or they keep extending and stay at the same club.
Look at the fees lukaku has commanded despite the fact he actually offers nothing outside goals, and doesn't score at a rate close to what haaland manages
The post I was replying to said that it's based on a team's need, but attackers are more valuable, so it's not as simple as players value being based on what a team needs.