The only major income from shirt sales is when people buy direct from the club or from the club shop. The cut on, say, a £60 adult Nike Liverpool shirt in general retail is likely in single digit pounds. Even if it’s £8 they’d need to sell millions of shirts to even make a dent in any wages or transfer fee if one is involved. While Lionel May take a pay cut (he’s apparently on up to €800k a week at Barca, possibly even after tax) that’s still tens of millions of shirts to sell if he’s ‘only’ on £500k a week.