Williams told the Lancashire Telegraph: "The worrying thing is that, as our percentage remains high, we're falling down the absolute wage chart.
"It's our lot in life to try to be as competitive as we can and it means we have to control non-football expenditure very tightly and we do.
"That enables us to pay a bit more in wages. We don't play other peoples' turnover, we play their wage bills.
"It would be very comforting from a balance sheet point of view, but we don't actually need the £20million for Roque (Santa Cruz).
"The problem is it invariably gets harder and harder to replace on a like-for-like basis.
"It's all about good scouting, selling high and buying low. Can we keep repeating that trick? I think we can but what we can't do is make a big mistake.
"You can make a small mistake, everyone does, but we can't go out and spend £5million on a player who isn't good enough. That would kill us because our finances are so finely balanced.
"If we can keep the profit and finances charge costs in line by finishing mid-table, our model suggests we can still be a trading club because there is no need to sell."