Most transfers these days are done in monthly installments over a number of years. Pompey now need the cash all upfront which means the price they will get will reduce screwing them even more due to being in a poor bargaining position.
Before they could sell a player for £10 million, £5 million upfront and £5 million over 3 years. Now they need it straight away, the same player may have to be sold for £6 million upfront and thats all in a take it or leave it offer.