Kindle file size = word count or pages?

In looking at Kindle books on Amazon, I haven't seen many (any?) with word counts listed. But they all have the kb size of a download. Is there any way to tell how long a book is by the kb size? How to know if it's a novella, an 80k novel, or a 120k novel? Or maybe it's just a 15k short story?

For instance: I was just looking at a Kindle version of a novel. File size says 167kb. One of the reviews mentions that it was quite short for a novel, about 50k.

Look at another book. A new Lee Child has file size listed as 5kb, and also says print length 416 pages (which corresponds to the hard cover copy). 5kb must be a typo?

http://www.amazon.com/Affair-Reacher-Novel-Jack-ebook/dp/B004P8JPS6/ref=sr_1_1?s=digital-text&ie=UTF8&qid=1315979906&sr=1-1

Tried another novel. This one on Kindle is 502 kb, mm paperback 368 pages.

http://www.amazon.com/Ghost-Ship-Chatham-Mystery-ebook/dp/B004CFB03K/ref=tmm_kin_title_0?ie=UTF8&m=AG56TWVU5XWC2

How do I know how long a story I'm getting for my $2.99 or $4.99 or $9.99 or whatever, if pages/word count aren't listed? Can I tell by looking at the file size, somehow?

I'm guessing whatever equation there is for Kindle won't work for other ebook formats ... smashwords or nook or the other file types.

So if the author/publisher doesn't list word count, is it just a crap shoot as to what I'm getting for the money???

Hmm. I guess for the same reason that if I went to a bookstore, and saw a short story on the shelf for $8.99, and then saw a novel on the shelf for $8.99, I'd think the short story was overpriced.

In print, it's fast/easy to see by looking at font size and number of pages. How thick is the spine? What's the page size?

Should it make a difference? Dunno. I guess it does to me for some reason, and it did to the reviewer who commented on my first example. He thought it was too short.

Maybe it won't matter after awhile of getting used to digital books? Hey, I wasn't fretting, don't think so. Just trying to figure things out.