When I wrote a piece late last year (access here), I noted that Etihad Airways hadn’t followed many other airlines and started selling its miles yet outside of up to 25% during redemption process.
Now, the airline is utilizing Points.com platform (most other airlines and hotel programs do the same) and allow members to purchase up to 100,000 Guest miles per year and up to 60,000 per transaction.
You can access Etihad’s page for buying Guest miles here.
Buying Guest miles:
The price of buying Guest miles is exactly two cents each.
Buying miles when redeeming:
When I just tried purchasing them during the redemption process, the price was 0.89 US cents each (when converted from AUD to USD).
Note that you can buy up to 25% of the required miles this way. In October last year, the price was exactly 1 US cent each.
You have to bear in mind that using Etihad own miles for Etihad awards is usually far more expensive than burning miles from American (usually 50% to 100% more expensive).
There are some bargains to be had (or at least were) with some partners. I have redeemed Etihad miles for short-haul flights within Brazil on GOL for example when fares have been expensive.