I've just had a look at the blank entry form and I can't see anything there that says fees are not refundable. You have to look at the Entry Fees section under Calendar Events to see that (and if you were looking for info about entry fees would it occur to you to look under 'Calendar Events'?). There are inevitably going to be some people taking the piss occasionally (quite infrequently from what jsabine says) but it wouldn't harm to have this stated ahead of paying, on the form or even on the event page. At least then people couldn't think they were entitled to a refund.
What's stated may be.
However, on the entry form that every entrant generates, it clearly states "
By signing this entry form you declare that you are insured as required. The event is run under Audax UK regulations. You should familiarise yourself with Audax UK regulations, guidance, and advice (available in AUK publications, at www.aukweb.net or on request from the organiser). "I don't want the topic to be a public debate on the shortfalls of the AUK system's and mechanisms, they have plenty of them to keep them gamefully employed.
John is correct when mentioning that this issue (which has been reported to AUK on three occasions) is a "non member" problem. And therein is where AUK board should be locked in a room, and not released until every payment shortfall is solved. FMEA/FMA call it what you will, is not an "enjoyable" task, but it does serve a very worthwhile function.
As FF's coda mentions. This is a complex subject that requires the use of more than one highlighter pen.