As I know a fair bit about One World Awards, through QANTAS Frequent Flyer points I will concentrate on those.
Based on my experience from other airlines including Star alliance and Sky Team however I have found most loyalty schemes are very similar.
The points value depends on what you want to buy.
Buying gifts or gift vouchers is the worst value.
I would get an email every week with offers from the Qantas gift shop to buy luggage, cameras, electrical goods,etc; using my points.
When I check the points against local discount store prices it looks like its around one cent (AU$0.01) for every 2 points.
About the only time I would look at buying something from an airline ‘shop’ would be if the points were set to expire, and I was unable to book a flight,
Buying an economy flight with ‘Classic Awards’ is much better value.
Although you will still have to pay Taxes and ‘Carrier Charges’ each point is worth between 1.5 – 2 cents (AU$0.015 – 0.02)
N.B. The points value if using ‘Points plus Pay’ is generally around half the classic award rates (not much better that gifts) although there is better availability of flights.
The best value on a strictly points for cash basis is either, buying Business Class tickets, or asking for an upgrade after buying an economy fare.
The cash equivalent of a point when spent like this can be 5-6 cents (AU$0.05 -0.06)
The problem is that very few Business Class seats are released for Frequent Flyers which makes them fairly hard to get.
When I had higher (Gold Status) it was easier to get upgraded tickets.
Understanding the value of points means you can better compare collecting points compared with other discounts you may be offered.