There's no moment quite as harrowing as seeing the youth star your club tenderly nurtured sold for a pittance, only to turn into a big-money world-beater worth millions of pounds a few years later.
Selling players is always a gamble, and parting company with a promising player too soon can often come back to haunt you further down the line. Then again, some clubs have perfected the art of selling their stars at their peak, and seriously reaped the rewards.
BettingsOdds.com have taken a look at every Premier League club's player sales over the last five years, and tallied up their current market values to determine the extent to which each club is either better or worse off since their sale, as well as their most unsuccessful transaction over the time period.
This is where Brighton & Hove Albion and the rest of the Premier League rank in the intriguing table:
9. 9th - Burnley - +£1.71m.
Amount received from players sold: £65.48m. Current value of sold players: £63.77m. Biggest loss = Jeff Hendrick - Amount received from sale: £0m. Value of player now: £8.1m. Difference: -£8.1m. Photo: Clive Rose
10. 10th - Leeds United - -£7.41m.
Amount received from players sold: £56.33m. Current value of sold players: £63.74m. Biggest loss = Caleb Ekuban - Amount received from sale: £0.9m. Value of player now: £4.95m. Difference: -£4.05m. Photo: Michael Regan
11. 11th - Fulham - -£17.79m
Amount received from players sold: £66.9m. Current value of sold players: £84.69m. Biggest loss = Moussa Dembele - Amount received from sale: £0m. Value of player now: £27m. Difference: -£27m. Photo: JAVIER SORIANO
12. 12th - Brighton & Hove Albion - -£26.28m
Amount received from players sold: £31.05m. Current value of sold players: £57.33m. Biggest loss = Mathias Normann - Amount received from sale: £1.53m. Value of player now: £11.7m. Difference: -£10.17m. Photo: Epsilon