So I figured that I'd go through how I'm assembling this army on the cheap for the benefit of others who are trying to collect an army whilst being frugal.  Here in Australia I've found that there are three easy ways to get cheap miniatures.

1. Trade/Buy Second Hand
Chances are you can often pick up what you're after for a good price if you wait around for it.  Perusing places like the WAU Buy, Swap & Sell forum can often net you a good bargain or two.  Other places are checking through what people have brought along to sell at tournaments or the local club.

2. Ebay
I buy a lot of my models off Ebay.  Almost all of my RT Eldar army has come from Ebay and hunting for deals.  I have found that the best bet is to watch a few sales to get an idea for how much things go for.  Put in you bid 48-24 hours beforehand and just walk away.  If you get outbid, just walking away is often the best option.  Early in the piece I found myself in bidding wars for stuff and ended up paying way more than I intended.  I use Hoard o' Bits for most of my bits orders but shop around for the best deals.

3. Buying Overseas
Due to the strong Australian dollar at the moment, buying overseas is extremely cheap.  I can buy stuff often for 50% off Australian RRP by buying from overseas sellers like Maelstrom and Wayland Games.

So lets look at how I'm assembling the force along with my initial guesses at costs:
Captain - $0 - Model to come from the Command Squad boxed set.  Halberd to be converted to represent a Relic Blade (Possibly from Chaos Knights models with iconography removed).
Librarian - $0 - I have an existing model so no need to source one.
Command Squad - $25 - To be purchased from Maelstrom Games, 4x scratch built Storm Shields, 1x Meltagun (bits box)
Drop Pods - $90 - 3x Maelstrom
Dreadnought Drop Pods - $5 - Scratch Built with drop pod bits added on for detail.
Assault Terminators - $35 - AoBR Terminators, 5x Thunder Hammers & Storm Shields, 10x Shoulder Pads (Ebay)
Dreadnoughts - $30 - 2x AoBR Dreadnought (Ebay), Heavy Flamer conversion (Witch Hunter parts from bits box)
Tactical Squads - $15 - AoBR Tactical Squad (Ebay), BfM Tactical Squad (Existing models)
Scouts - $0 - Existing Models
Land Speeder Storm - $25 - Maelstrom

Land Speeders - $50 - Maelstrom
Other Bits and Pieces - $10 - Transfers etc

That brings me to a total of $285.

Currently I've sourced the following from Hoard o' Bits over a period of three weeks of bidding:
2x AoBR Dreadnoughts - $30.00 + Shipping
AoBR Terminators, 5x Thunder Hammers & Storm Shields, 10x Shoulder Pads - $21.30 + Shipping
AoBR Tactical Squad (Ebay) - $10.50 + Shipping
Transfers - $2.00 + Shipping
Shipping - $5.30

Total: $69.10

This puts me quite a bit under so far, with only the dreadnoughts actually costing my close to my estimation, but I can't save much on the Maelstrom Order.  I do however have some unopened prizes from tournaments that I hope to trade in for a box or two of things that I need.  So far so good, the only downside being that moving means that I'm getting this stuff shipped to my Parent's house in Rockhampton and will have to find a way to get them down to Brisbane after they arrive (which will probably cost more than the shipping costs to get them from the US).