Clubs were trying to contain cash outflows before COVID; but clearly shit hit the fan this summer and the one before.
Looks like the EPL clubs stopped their transfer business with the Championship clubs this summer - hence the dramatic fall-off in income (green). For the most part, Championship clubs buy from each other or from lower leagues.
In terms of trickle down ... nothing is trickling down any more.
I expect that all clubs are in tight cash flow conditions. Therefore, cash is not flowing to pay for transfers and the only way the selling club can receive cash now is to factor the receivable from the buying club. Of course, there is a discount to the amount received in that process. These transactions typically result in filings at Companies House. I am waiting for the Swans filings for Lowe and Roberts, then we will know what the Club received.