I made a "promise" yesterday

and I now realise I may not be able to keep it. I made it reluctantly but in good faith.
One of the (very) extended clan contacted me and said, "Cat, there's this writing competition you must enter!"
Now, as Nicola Morgan would tell you, I have a "thing" about writing competitions. I do not like them.  I regard them a bit the way I regard exams. 
Exams are not a test of what you really know but a test of what you know at a particular time about the topics an examiner has chosen to ask you. The marking of them can be reasonably objective - in subjects like mathematics - or very subjective - in subjects like English. Although all sorts of things get tried from time to time there is really not an answer to the problem of subjectivity. The best that can be said for most exams is that they give other people some idea about what you know and what you have to say about it.
"Competitions" are even worse. It must surely be rare for the judges of a competition to agree with each other - and then have that great critic "The Public" agree as well. Let's face it, the vast majority of people enter competitions because they believe, whatever they might say, that their work is worthy of a prize - preferably first prize. The vast majority of people are also disappointed. They do not win prizes but, like gamblers, they keep on trying. They tell themselves that, this time, it will be me. 
So, yesterday the distant member of the clan contacted me about a writing competition, or perhaps I should say "the" writing competition. I need to explain at this point. The competition bears the name of a highly regarded Scottish author and member of the clan. The author is, of course, deceased but his work sits among the classics of twentieth century Scottish literature. There is a biennial competition for a short story, poetry - for adults and schools. Apparently it behoves all clan members who write anything to enter it - or so the distant member of the clan has advised me. I do not believe that but he made me give an undertaking to try. He knows that, unusually for me, I have a short story almost complete - and that it fits the theme of the current competition. (I was foolish enough to mention this fact as an excuse for not doing something else.) Entries must be in within the next two weeks. The writing will probably be finished within two days. There is no excuse - or is there?
So, what's the problem? Well, there is the small matter of how to pay the entry fee. There is an entry fee of seven pounds. In the United Kingdom this would not be a problem. It would not be a problem if the organisers had Paypal facilities but the entry fee must be paid into a bank account, by cheque or money order.  If I had a credit card I might - just might - be willing to pay the exorbitant bank fee of twenty-four dollars for sending that sum. As it is I do not have a credit card. I would need to go to the bank and pay thirty-two dollars to send what currently amounts to about twelve dollars. I object to that. I object to banks charging those sort of fees - especially for transactions which amount to nothing more than a flow of electrons where the customer does the work.
The question - is that a valid excuse for breaking my promise to enter the competition?