£32m for Berbatov at the time was big money, bear in mind we only got £32m for Modric several years later, and that was after the Kaka and Ronaldo sales that began to warp perceived value of transfer fees, Berbatov moved before that when the record fee was still around £56m for Zidane. Also think you're going a bit tin-foil hat with the assumption that Liverpool and (especially) United at that time were buying off us specifically to weaken us, suspect their reasons were far more in line with what our own would be if we were targetting a promising player at a perceived smaller club that we were confident of luring; they're proven in your league and you can be relatively certain they will hit the ground running. Of course one could argue neither Keane nor Berbatov necessarily proved that perceived logic to be true, but they wouldn't be the first or last to confound that logic.Our problem with Berbatov and Keane is both wanted to leave and neither ManU or Liverpool wanted to pay much for them so it got dragged out to end of window (not our choice), so, as you say we reinvested in January (including re-signing Keane if I recall right as his move to his 'boyhood club' didn't work out so we resigned at a slight discount to his price to Liverpool).
BTW I think ManU and Liverpool mainly wanted the players as Spurs, with those 2 attackers' wre a big threat to them. So their buying tactics were designed to disrupt Spurs as much as possible, hence the very late deal for Berbatov for £30m was , despite ManU's moans, a low price for a very good striker. However he never thrived at ManU as he didn't fit their side ...... one of the results of the buying being a disruption tactic rather than actually identifying and buying the best striker for their side.