You know it's a transfer window when the X + Y = ZZZZZZZ discussions come in. In short it costs a shitload of money to sign expensive players. Seems obvious, but salaries, signing on fees, and agent fees are mostly ignored. Then you have the issue of being bent over a table any time you try to sign an important player during the January transfer window.
We know our position now. We can make perhaps one signing in this category per season, especially in the position we are now, but before...nah, not really. The squad would be super light, and these are investments.