The cheapest ADSL or Cable net access in Australia seems to be about $30 per month. I’ve been using 3G net access by the “Three” phone company for 18 months now and it’s been working well . I recently bought a new 3G modem because the old one broke, so it has cost me $250 in modems plus $15 per month for the connection which compares well to $100 (or more) for an ADSL or Cable installation plus $30 per month.
My Three net access gives me 1G of data per month. I have just noticed that they have pre-paid net access that gives 12G of data that must be used within one year which costs $149 per year  – that is $12.41 per month or 83% the price of the plan access plus it means that any bandwidth quota that isn’t used in one month can be used the next month (so you can save up for upgrading to a newer distribution of Linux).
Dodo has pre-paid mobile net access on the Optus network for $139 which gives 15G of data that must be used within one year . So that’s equivalent to $11.58 per month or $9.20 per gig.
A member of my local LUG mentioned that Exetel has a 3G plan which is good value if you don’t use much data transfer – but which has per-megabyte charges for excess data transfer. I couldn’t recommend it for my parents as I never know when they will do something that may transfer a lot of data, I could just imagine them saying “loading web pages was really slow for a week and then I got a big bill”.
Ross Barkman’s GPRS/UMTS page gives some critical information on using a 3G phone with a tether . Using that information I discovered that I need to use “AT+CGDCONT=1,"IP","3netaccess"” in my chatscript to get ppp going with my old LG U890 mobile phone (with “3netaccess” being the important word).
I plan to give my old mobile phone to my parents and let them use prepaid 3G net access to reduce their net access bill by more than 1/3 while also giving them more data transfer quota for times when they need to transfer a lot (EG when my sister visits them). At this stage I’m not sure whether I will get them to use Three or Dodo. One advantage of Three is that I’ve used them a lot and know exactly how to get it all working, the other is that my old mobile phone is locked to Three – they agreed to unlock it on demand after the contract is ended (which happened over a year ago) but it will be a hassle to get it done. Saving the hassle of getting an old phone unlocked may be worth the $10 per year cost. Also I have used my 3G modem at my parents house on a few occasions and know that the reception is quite good, while the reception for Dodo (Optus) 3G is unknown
One extra benefit with doing this is that my parents will have some freedom to move their PC. If they decide that the computer room is too hot in summer and want to move their PC to below their air-conditioner they will be able to do so without needing a long Ethernet cable to connect their PC to the cable modem.
For my personal 3G net access (which I require for fixing servers on occasion) I am stuck with Three. When I bought a new 3G modem I decided to save about $20 by getting a device that’s locked to Three. 12G per year is more than enough for sshing to servers and checking email and if I had paid extra for the unlocked modem it would it would probably have died before the savings on net access made up for the higher purchase price.
Crazy John has a good deal, $129 for 7.5G which expires in a year . I won’t use that for my parents though, the probability of them going over 7.5G is too high to make it worth the risk for a $10 saving.
-  http://etbe.coker.com.au/2008/07/28/new-net-connections/
-  http://www.three.com.au/cs/ContentServer?c=Page&pagename=Three%2FPage%2FBusinessVideoCallingTemplate&cid=1221530707570
-  https://secure.dodo.com.au/prepaid-wireless/PlanSelection.aspx
-  http://www.taniwha.org.uk/gprs.html
-  http://www.crazyjohns.com.au/mobile-broadband/