The reference to buying separately in the games listing has gone too. The postage is probably a little steep in that listing, but I'm really pleased to see that the OP is trying to fix his listings up.

Ricky, when working out the postage, it can help to use the Aust Post postage calculator. If an item has a packaged weight of under 500g, then it will cost $7.40 to post anywhere in Australia as a parcel (it's slightly more if you use a satchel). I have no idea how weighty PS games are but they may well come in at under 500g even when packed. As sellers pay a fee on the postage cost to eBay, most sellers will charge a bit extra to cover those fees and also packaging costs. Charging $8 or $9 isn't unreasonable if you have to buy new packaging to send. Any more than that and buyers may well either not buy, or ding your feedback and postage stars.

Charging nearly $25 for posting those games would be a big turn off for most buyers (even if they are getting them for a bargain). Invest in a set of cheap digital kitchen scales (under $20) and you can weigh your items before listing so you can have a more accurate postage cost showing. Anything under 500g you would list as "same cost for everyone" and you insert the amount you want to charge. Anything over 500g, like the PS, you'd use calculated postage, which means buyers in different states will see a different cost. Sending to Perth could work out expensive if it's over 1kg, so if the box can fit into a 5kg satchel, then it could be sent that way as a flat rate cost to anywhere in Australia.

Have a look at the AP site to see what's available and put in different locations and different weights to get an idea of different costs.