Im looking at a DONE4 next year (possibly February) and using the pricing on the qantas site, it would appear these are my options in terms of price (excl taxes) in AUD$:
ex Australia $9539.00
ex India $8364.00 ($7298 + $1066.00 for return ticket)
ex Egypt $8277.00 ($6761 + $1516.00 for return ticket)
ex Thailand $8245.00 ($7597 + $648.00 for return ticket)
ex Pakistan $8104.00 ($6766 + $1338.00 for return ticket)
ex Turkey $7952.00 ($6489 + $1463.00 for return ticket)
ex Sri Lanka $7486.00 ($6503 + $983.00 for return ticket)

I now have a couple of questions:
1/ Are there any hassles with buying and collecting a ticket out of Colombo ? Can it be collected at the airport ? Or is Istanbul better ?
2/ Would it be better to buy a one way ticket Australia to Sri Lanka/Turkey rather than return and then try and finish trip in Australia by not turning up for last flight segment (which would be Australia-Sri Lanka/Turkey)
3/ Any suggestions on the following itinery with the above in mind ?
CMB-HKG-NRT-JFK-MIA-DFW-ANC-DFW-BOS-LAX-LHR-DXB-LHR-MEL-PER-CNS-SYD-HKG-CMB I would like to get to LAS if possible (not worried about ANC or BOS) but also want to maximise mileage out of the trip and if I could get a cheap one way to Sri Lanka/Istanbul would not be using the SYD-HKG-CMB segments.

Any thoughts ?

I'll take a stab at your questions - and I am sure others more expert will chime in.

I've bought my last two RTWs out of Egypt, so can't speak to either CMB or Istanbul. I am buying a ticket ex-CMB from the CX office and have found them to be a pleasure to work with (albeit on a simple ticket). Others have posted satisfactory experience in buying tickets ex-IST.

I generally find it easier to buy a one way - or a RT ticket that is likely to be used only as a one way - as my RTWs tend to sprawl across much of a year. It is easy to know my start date; I never know my end date.

Buy a ticket on WN from LAX to LAS on their website at www.iflyswa.com. WN has frequent service, and their prices are often the best available.

Keep in mind that you can use the final segments of your ticket up to one year after the originating flight. You might find RTW travel addictive, and decide to get a second RTW. And if not, I have never heard of any consequences for failing to use the final coupons on a RTW.