From the AA website Australian version;
SFO-LAX one way on instant upgrade is currently selling at AUD$159.00 not all flights available at this price; that will get you 60SCs per hit; for something different you could try SFO-LAX-LAS for $382.00 one way on an instant upgrade, that should nett 120SCs.
There are other options available you just need to do some searches; flights up to SEA can also be worthwhile and the flying in on AS but you need to have an AA flight number in the booking.
LAN across to New Zealand is good at about AUD $700 return netting 160SCs. One way LAN from NZ is currently AUD $300 netting 80SCs due to pricing in NZ dollars.
Check where Virgin America or any other low cost carrier is flying (others to check are Jetblue and Airtran) and see if AA are matching.
I think Serfty retained platinum in 6 days, basically flying all the way to NYC then flying to Hawaii and back and Florida and back, plus a bit in between.
I think if you can get it for $5,000 you are doing well but a friend has flown for 6 days across country and back for just over $2,000 and netting 1200SCs:shock:
Searching the forum is good and reading what Serfty has to say, as he has usually flown it and can tell you about it.
Do you really enjoy flying that much and want to retain Platinum, do you have the spare cash and the time; for some the answer is yes.
I enjoy flying would love to reach platinum but I have neither the money or the time so I just have to read what is written here, stuck on lowly Bronze. :-|