West Ham don't even pay for the running costs for operating on matchdays do they? The stadium situation is undoubtedly a big financial advantage for them and they threw cash around before that anyway. If you are looking to compete further up the table then £30m is a pretty standard price. Sure with Broja you're paying a lot for potential, but what did they spend on Haller? £40/50m something like that. He was 'proven' and didn't work out so I don't think £30m on Broja is that much of a risk for them financially even if he doesn't push on and live up to his potential.
There is a surprisingly level headed post over on Saintsweb about some of the 25m+ signings in recent years from outside of the top 6. It might be cherry picked but it is actually quite grim reading. There are very few that are unqualified successes. I think the two picked out specifically are Jiminez and Tielemans - both had a loan before hand. And there is something fishy going on with Wolves and their transfer arrangements anyway.
It is a little like this idea that people seem to have about how many players are on 100k / week or more. Outside of the Top 6 it really isn't as many as you would think if the data that is out there is true. And even with some of the top 6.
So when people on twitter were claiming that West Ham would "comfortably" offer Broja at least 150k a week (making him their highest paid player and one of only 3 or 4 on more than 100k a week) or that Spurs would give JWP a massive payrise (when we are paying him similar to what they are paying Hoj) you know that they have had their views distorted by the Manchester clubs, Chelsea and Liverpool
Edit: The 31m+ signings are kind of 50:50 although some are quite recent so jury is kind of still out. Transfermarkt top signings stopped at 31m. I think it is when the 25m get included that the "hit" rate could well go down as you get people like Brewster
Haller (West Ham) - 45.00m
Sigurdsson (Everton) - 44.46m
Tielemans (Leicester) - 40.50m
Joelinton (Newcastle) - 39.60m
Bruno (Newcastle) - 37.89m
Fabio Silva (Wolves) - 36.00m
Richarlison (Everton) - 35.28m
Buendia (Aston Villa) - 34.56m
Jiminez (Wolves) - 34.20m
Anderson (West Ham) - 34.20m
Lukaku (Everton) - 31.82m
Aguerd (West Ham) - 31.50m
Zouma (West Ham) - 31.50m
Fofana (Leicester) - 31.50m
14 in there. I'd say 4 unqualified successes (Lukaku, Richarlison, Jiminez and Tielmans). Two of those based on successful loans
2 likely to be considered successes - Zouma and Fofana (injury considered). Bruno looks like he will be.
At least 5 in there where if we spent that and got that return it would be at least a massive let down and at worst a disaster