I think its make it up as you go along.
Influencing factors likely to be, nature and size of those charged, and media furore that could follow . Saints or smaller well hit 'em hard make an example of them , Chelsea/Man City ... 'well we thought we'd impose a token fine, just to send a message out and being seen to be doing the right thing... if that's alright with you that is.... although on reflection we could reduce it a tad ...'