Just to double check, a quick search turned up this article
with an average of around $100 and a recommendation to throw them out at 500-600 miles. 16 to 20 cents a mile. For reference my "serious" running friends are into it at about 30 cents a mile.
The Sports cost me around $80 altogether (including new tires and tubes) and at that time I had about 2000 miles on it. That's between 4 and 5 cents per mile - if it disappeared on that afternoon. It has more miles on it now, and I've also replaced some other bits (grips, brake pads, cotters, etc). More than half of the miles have been commuting or errands. It's been a pretty good value for me. I rode it on the 25 mile round trip commute last week, so it's still turning "revenue" miles.
If I sold the bike for $50, the cost per mile would go way down. I wouldn't expect shoes to retain much value after 1000 miles .
The newer more (ahem) "specialized" bike I bought for commuting has not been economical, taking a new fork (recall), a new rear wheel (cheaply made), and new tires and some other things. It has been more expensive than walking, FWIW.