It seems to be the new fashion to reject the net spend argument as being of no importance, and of course to a large extent, depending on the circumstances, it is entirely feasible to significantly improve a squad with minimal or negative net spend.
I think for us though, the more pertinent consideration is that we are now trying to play catch up after 30 years of standing still/going backwards with clubs that have spent literally billions in that same period, most notably the last 10-15 years.
It's hard to see how we cannot narrow that gap without considerable net investment, even if that is over the course of only 1-2 seasons, to put us on a surer footing from which we can build.
Much has been made this summer of our big spending, but in absolute and relative terms it means little. In the earlier part of the summer the club deserved and got much credit for the efficiency of execution, but to a large degree of chances of improving our league position and doing better all round rest more or less entirely on getting the additional players that Koeman has identified.
There is probably another £100m required to sign Sigurdsson, a striker, and a left/centre back. Even then we should be able to recoup at least half of that on sales so the extra push shouldn't really be too much of a drain on the clubs resources. You never hear the elite clubs fans talking about net spend as its simply irrelevant to them.
There may now be a model for making profit on player trading, but its easy for clubs like Chelsea to be able to go down that route in the first place, with the huge advantage they had in being able to fork out enormous sums of money for players pre FFP, and hoarding players like nobodys business. I'm open to correction here, but I think they spent £115m or thereabouts on new signings in 2003, the first year under Abramovichs ownership. It is sobering to reflect on that 14 years later as an Evertonian given the much vaunted attention given to our £100M "warchest".
Not saying the club hasn't done well this summer, and still confident that they'll deliver more by August 31st, but they simply have to, both in terms of delivery of deals and resourcing fees.