Comply Foam Tips are currently having a 4th of July promotion - buy 2 (packs of 3 or 5 pairs) and get a third free. You can further apply the 20% discount code.
For example I bought 3 x 3 pairs of T-500 for approximately AU$44.40 shipped, $4.93 a pair.
The cheapest local stock is $9.65 a pair from eBay.
They are available in black, blue, red, and platinum from Comply. Local sellers seem to only have black.
Note: their shopping cart is a bit buggy. In order to get the coupon to deduct the full 20% I had to:
1. Add 2 pairs to cart.
2. Apply the coupon.
3. Add the 3rd pair to cart.