If I had to do it all again there are a few things I would do differently to save our cash and I'll list them as we go so maybe you'll benefit from the lessons of my mistakes.
Then we put them in just the one cot until they learnt to roll over, so we really didnt need two cots for quite some time!
Next you need to think about linens. You'll need 3 sets of bassinet sheets and 3 sets of cot sheets each. If you intend to use the bassinets only at first for sleeping then you won't need the cot sheets up front. I bought about 6 sets of cot sheets EACH! Why, I'll never know? We've never used that many. To begin with 3 sets was enough since they shared the same cot. Later we have needed the 3 sets each (especially when we've had times of illness).
As for blankets, once again I purchased WAY too many and then went out and bought baby sleeping bags anyway since they are safer for baby to sleep in. Depending on when your babies are due and the season (keeping in mind the possibility of premature birth with multiples) just buy a couple of blankets to start off with. Avoid fleece as small amounts can be pulled off and ingested by little ones. Cotton blankets are best, teamed with baby sleeping bags or swaddling for adequate warmth.
I've never used bumpers or any other padding around the cot and was actually quite paranoid and took the mobile down every night just in case it fell into their cot while I was asleep. :) Having premature babies put me on high alert for the risk of SIDS so I wasnt taking ANY chances!
We also purchased TWO baby movement and sound monitors. For whatever reason, we never used the movement plate of the monitors and so we only ever used ONE of the monitors for sound only. The twins slept in our room until around 6 months old so I just felt we didn't need the monitors on. When they were in their own room (and still even now) we use one monitor just for sounds. This is completely a personal choice and will depend on what you feel secure with in yourself.
On the subject of saving dollars... secondhand cots can be found quite easily (try ebay or your local classifieds) and often in very good condition. Just be sure to check that the cots meet the current Australian standards as many of the older models can be quite dangerous as the slats are too wide and baby can get their head stuck or they may have paint which can chip off and be swallowed or the paint used may actually be quite toxic.
Next post I'll talk about purchasing clothing for your twins...