There is a point where the additional benefit of Hamers' extra quality is bettered by having more of other players paid for by the transfer fee earned by selling him. If £1m bought Walker and £1.5 bought Hamer in the first place, clearly even £3m gets you two or even three quality players. And makes you less reliant on one man.
Doubling our money in only 12 months, by any measure, would be good business normally. However in a competitive market we have look for more than that. Who knows how to value footballer, least of all us lot, but £5m must be the starting point.
There is no point selling him in January, assuming we get a bid, unless Covid is really clobbering us. His value can only rise, and a sale now jeopardizes the fight against relegation, so would be shooting ourselves in the foot.
In short - max on the cash in summer - particularly the up front money - fill the gaps for next season - left wing back, central defence cover, attacking midfield.
Maybe even flog Godden and put that money down as a contribution towards getting an upper-Championship level striker.