Solid state drives are coming down in price, but it's hard to beat magnetic media when it comes to bang for your buck. SSDs are also not the best for backup purposes, where their limited write cycles and high cost make them poor substitutes for good old HDDs. If you're in the market for an external backup drive, Officeworks might have what you're looking for.
The retailer is currently selling HP's 2TB SimpleSave drive for $109. It's compatible with USB 3.0, so your future-proofing needs are covered and with 2048GB of space, you should be able to cram just about anything onto it.
Here are some of the more important specifications, from the Officeworks product page:
USB2.0 / USB3.0 compatible. Three years limited warranty. Dimensions: 130 (L) x 54 (W) x 169 (H) mm.
It requires an external power pack, but that's to be expected for the price.