I'm not sure if this is considered a hack, but it is something I have been doing for a while. It only applies to Woolworths (not Coles) and only for online orders.
Woolworths has an unadvertised rule for weight-based items (that are not pre-packaged in a tray). The rule is, they have to give you more than what you pay for.
For example, if you buy 100g of ham and one slice of ham is 75g, then they have to give you two slices, which would be 150g and you'll only pay for 100g.
This deal works better with sliced meat, as opposed to shaved meat, because each slice weighs more.
Say if I want 300g of ham and I'm not fussy about which type. Instead of buying 300g of ham, I'd buy 100g of one type of ham and 100g of another type of ham. I usually end up with around 300g of ham and only paying for 200g.
Note: This also works with other weight based items that are not prepackaged where you have to purchase by weight, e.g. in 100g lots. The amount of saving depends on how chunky the item is
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