Earning points and discounts for shopping on eBay
For Australians shopping on eBay, there are four major options for earning points or getting a discount via cashback. The rewards are relatively small, but it is a simple case of earning extra points for just logging in and clicking a button to get the benefits. In that sense, it is worth the additional 30 seconds when buying items from the eBay site. For a small purchase like $5-10, some people may not bother with the extra step, which is fair enough. However, you can earn a reasonable haul of frequent flyer points or discounts if you plan on making more expensive purchases.

Which option you choose will come down a choice of Virgin or Qantas frequent flyer points, or a discount through cashback. Since you don't get any perks for spending more or being loyal to any site, there is no problem with spreading your points or cash earning options across different purchases if this suits your needs. Also be on the lookout for specials that are run at various times where the offers are substantially increased for a limited time.

The new player in earning benefits through shopping on eBay is FlyBuys. They have sent out targeted offers to their customer base and even though it may seem appealing, it is the worst for earning benefits. At the time of writing (November 2017), there was no way of taking advantage of the Flybuys offer unless you were directly emailed to join. If you've missed out, there is not much to fret about. As you can see below, it is the worst value of the four options for earning benefits through eBay.

Bonus tip 1
Points on frequent flyer programs such as those run by Virgin (Velocity) and Qantas will not expire as long as your account has some activity. This means you will lose all your points if you haven't been active for 24 months (Virgin) or 18 months (Qantas). Making a small purchase using the airline's ebay links will allow you to keep those points for another 12-24 months. Just keep in mind that it takes 30 days after the eBay purchase for the points to be credited to your account.

Bonus tip 2: save a further 5% on eBay purchases
You can save another 5% by using Woolworths gift vouchers. For more details see Save over 6% on any eBay purchase by combining discount offers.

How it works
You may be curious as to why airlines and Cashrewards are offering these bonuses. Companies can earn a commission for directing you to the eBay site. The airlines use points as incentive for you to follow their links (and therefore earn themselves a commission), whereas Cashrewards returns some of that commission back to you. This money returned to you is effectively a discount on what you buy. Login or sign-up here with a free $5 credit new window at Cashrewards. You won't pay more for following the links, so it's worth investigating.

One caveat to watch. If you click different sites to earn points on eBay, only the most recent one that you've clicked will be credited. For example if you clicked Virgin's eBay link first, then later clicked on the Qantas eBay link and eventually make a purchase, the points will go to your Qantas account. As an extension, you can't attempt to click on all the links in the hope to earn across the all sites for a single purchase, only one account will be credited for each purchase.

For this comparison, we are valuing frequent flyer points at 1 cent each. As you can see below, in terms of value received, Cashrewards is the clear winner (1.3% cash back), followed by Virgin and Qantas (1 point per dollar) and lastly FlyBuys (0.435-0.5 cents per dollar spent).

Rewards per dollar: 1.3 cents cashback (but this can vary from 1% to 3%)

How to earn points: log in to Cashrewards new window, search for eBay and click the Shop now button.

Rewards per dollar: 1 Velocity frequent flyer point worth 1 cent

How to earn points: You will need to visit the eBay page at Virgin's eStore new window and log-in to your Velocity account. Search for eBay if you can't see it, click the Start shopping button and you'll be redirected to the eBay site, then purchase as per normal.

Rewards per dollar: 1 Qantas frequent flyer point worth 1 cent

How to earn points: Visit the Qantas Online Mall and log-in to your Qantas account. Search for ebay or follow this link new window, click the Shop Now button and you'll be redirected to the eBay site, then purchase as per normal.

Rewards per dollar: 1 FlyBuys point worth 0.435-0.5 cents

How to earn points: you must be invited to join the program and link your eBay and FlyBuys accounts. Be warned though, this is the least valuable option for earning benefits through eBay, especially for those looking to earn Virgin Velocity points. By using the Virgin direct link to eBay described above, you earn 1 Velocity point per dollar. However, 1 FlyBuys point earns only 0.435 Velocity points, and these can only be redeemed once you have 2,000 FlyBuys points. The option of getting the $10 Coles voucher through FlyBuys values the points earned at 0.5 cents per dollar spent at eBay (2,000 FlyBuys earns a $10 voucher). In this case, the Cashrewards option offers at least double the value.