Yarralumla is a great location but it does not have a large stock of 1 bed 1 bath 1 car space type properties, so I could not say it is particularly cheap and would doubt that it is. Suggest you look at allhomes.com.au for more of an idea on pricing and availability.
It does seem pretty expensive, but with the houses I've found searching around on different websites, it's worth it. Some can be up to 2,400 dollars, and other can be only 100 dollars. What i'm trying to say is that you get what you pay for.