Define long layover, 4 hours? 10 hours?
If it's a 4-5 hours layover then Emirates J lounge access can be purchased for ~$130 USD (which is ~AU$200). Personally I think this is not terrible value at ~$50 per hour (especially given the higher price of food/alcohol in the terminal - a couple of glasses of champagne could easily equal this amount).
Another cheaper option would be a 3rd party lounge. I hold a free dragon pass membership via regus (more details at this link I found on google
Tutorial: Free Dragonpass Membership plenty of other articles with the same info just the first one I found).
This allows for Dragon Pass access at £19 (~AU$35) per person per entry. In Dubai there are 13 lounges a part of Dragon Pass noting that most have a 3-4 hour limit however noting stopping you from entering one for 3 hours and then paying another £19 for another 3 hours elsewhere or at the same lounge. Happy to answer questions about this.
Finally if the layover is a really long one then I'd consider either going out and exploring Dubai or getting a room. The airside hotel starts at ~$350 for an up to 12 hour stay otherwise if they are able to enter the UAE many other hotels nearby offer rates around $100-200 for either a day or night.
The metro runs every 5 minutes during the day and takes 25 minutes to get to the Bruj Khalifa (plenty to do nearby to kill time).
