My wife trawled garage sales when our first sun was born. Best buy was a Macpac possum (like this, but an earlier model:
Macpac Possum Baby Carrier Reviews Australia www.macpac.co.nz)
The lady selling it had been given it when leaving a job to go on maternity leave and had
never used it (it was still in the plastic bag from the shop). My wife paid $100 for it (these retailed about $300) and we used it a lot, before selling it on ebay (5 years and two boys later) for $96 dollars.