I agree with ficbot [
https://www.mobileread.com/forums/sho...6&postcount=3] on this: forget the cash out of pocket -- my time is more valuable. So, I give myself permission to "bail".
Still, something has to be pretty dreadful (to me) to quit part way through. If I am experiencing heavy weather, I will sometimes switch to something else for a few days. But if I've put something aside for, say, 30 days, odds are low I will ever return to it.
I've also been reading for a few years now ...
so while I certainly try to stretch, I also have a reasonable idea if the synopsis or sample chapter appeals. I've probably bailed on 2 titles since re-discovering reading with my Kindle 2 in Nov 2009 .. and I've read about 50 books since. I can handle 4% "loss".
One final point: while I am not first in line to buy a $20 e-book, the law of averages is ok for me. My total ebook spend averages somewhere around $4 (some books free, some library books, some closer to $10 or occasionally more) ... so bailing even on an "expensive" title gets averaged in to what is overall a relatively inexpensive and very satisfying hobby: reading for pleasure.