We paid £15m for Hamer, and got 120 or so games out of him before selling for less than half what we paid.
We paid £23m for Brewster and his contributions helped us get promoted to the PL in 22/23.
We paid £17m for McBurnie and his 13 goals helped us get promoted in 22/23.
We paid £8m for Mousset and his goals contributed to Sheffield United achieving our highest league finish in anyone's recent memory.
And then your convenient omissions:
We paid nothing for Brooks, he sold for £8m. We paid nothing for Lankshear, we'll likely have made something like £4m off him cumulatively. We paid nothing for Brooks (D). We paid nothing for Peck who'll go for £10m-15m.
Player purchases are primarily about making the team better for the now and the immediate future. For the most part, players don't sign contract extensions because their earning potential as higher than the extra we can evenly offer them.
This is the reality of football - money spent on transfers is a sunk cost we shouldn't expect to get back.