As I detail above, with a few more realistic assumption, you can get an estimate of word count from file size that isn't going to be off by orders of magnitude.
You cannot help yourself, can you? You see an opportunity to post something contradicting what someone has said, and you can't resist.
It doesn't matter to you if someone was attempting to be constructive, even if they were exceedingly polite towards you.
This is how I started and finished the post I made that you somehow managed to find a nit-picking way to contradict:
My GUESS is the page count is the more reliable of those two figures.
To @DS ... WE AGREE ... the page count suggests about 60,000 words. ;)
WHY would anyone here even bother trying polite to you after seeing the shit you came up with responding to that.
The point the rest of my post was making was that page size was more reliable to derive an estimate - it's reasonable to assume a page size of about 300 words, but there's no way of knowing how inefficiently Amazon stores it data.
Why couldn't you attempt to be constructive, and provide some estimate for how many words per KB Amazon might be using? The answer to that is simple ... You enjoy being a pain in the ass/arse to others too much: it is you raison de'etre!
Now after being challenged you've come up with some "calculations". They are COMPLETE BULLSHIT.
It does not matter if Amazon does actually does store its data that way ... your calculations are nothing more than guesses about what they do. You have ABSOLUTELY no way of knowing of they are true or not. You have, in fact, only applied you invented, after the fact, until you got the answer you wanted!