I don't have a problem finding audiobooks to buy at Audible even though I avoid those I can get at my public library (which has over 10,000 mp3 audiobooks). I bought today's daily deal, that's my 3rd this month. I usually buy 3 or 4 Audible daily deals a month plus the occasional Whispersync for Voice match to go with ebook daily deals or sales. It helps that I'm buying for both myself and my husband; we like different genres so that doubles the probability of hitting the daily deal lotto.
I'm buying at a considerably faster pace than we are listening, but for a few bucks a pop it's worth it to have access to a large library of listening choices. Plus most of the $ I spend on these daily deals comes from promotions and not out of my pocket.