I don't think this is true - football clubs will nearly always try to at least recoup part of the transfer fee paid for a player. So whilst Ashley-Seal has been very disappointing they likely wont let him walk for nothing. Can't quite believe you wouldn't expect significant fees for Horsfall, McWilliams or Chuk!
Also I think people are overly critical of Sowerby, at times he played well. We should see improved versions of him, Mills, Rose etc. this year as they will likely know they underperformed and will want to put it right.
I agree with you about Horsfall, McWilliams & Chuks though think the club would count their loses with BAS, let him go for free and move on.
As for Sowerby, Mills & Rose, they were three of the poorer players in a team not good enough to stay in league one. For me they are bang average league 2 players, if we want to get promoted we will need quality around them, unless they dramatically improve they don’t look the difference makers for us to go up.