Amazon Prime Overnight Shipping Deadline is earlier

I've belonged to Amazon Prime for a year - the $80 per year program that gets you two-day shipping for free and overnight shipping for $3.99.

However, Prime overnight shipping doesn't quite play by the same rules as regular overnight shipping. To get an order shipped overnight under the Prime program, I apparently have to order it by 4:30pm. (I'm in ET; I don't know if that makes a difference.) But for non-prime users who want overnight delivery, they can order up until 6:45pm. (The two-day ordering deadline is still 6:45pm.)

Granted, the costs are considerably different. If I order Stephen King's Lisey's Story overnight using Amazon prime, it costs me an extra $3.99.

But if don't have Prime and I order the same book overnight, it will cost me $12.49 + $3.49 for each book, or $15.98. That's $12 more for another 2:15 of procrastination time.

It's a trade off for Amazon; presumably having an earlier cutoff reduces their costs, and Amazon Prime shipping is reported to cost them a lot of money. But it's a change that I've never seen mentioned by Amazon - I'm pretty sure the cutoff wasn't as early as 4:30 when we signed up. And if you pay your $80 and expect the same service, you might be disappointed.

2/8/07 Update:

The story seems somewhat more complicated than that. Today I ordered an overnight item using Prime, and it claimed I had until 6pm. I checked the Stephen King book I mentioned above, and though yesterday I had until 4:30 to order it, today I have until 6:45. Another item gave me until 6:15, and the same order without prime was also going to ship at the same time. Hmmm. Further more, Amazon only charged me $1.99 to do one day shipping, not $3.99.

I'm guessing the cutoff time is related to how available the item is, or perhaps how close the item is to the buyer.