I love the keto diet but alas, the food requirements are so expensive, I just can’t afford to keep on it
Being aware that you are in Australia, not the U.S. (with some of the cheapest food on earth), I would suggest that the expense depends in part on what kinds of food you're buying.
As I look at other keto support forums, I see a number of them do some "gatekeeping" -- an insistence that one cannot "do" keto properly without organic grass-fed beef, pastured chickens and eggs, cold-press virgin coconut oil, etc. And it's not true. A person can do keto just fine with "cage" eggs, cheap sausages, the least expensive butter and olive oil in the market, and so on.
Not to chastise anyone or shame them for what they can (or choose to) spend on food; just noting that some "experts" put up artificial barriers to following a keto eating plan.
Personally, I think if a person can lose weight with keto, that lost weight and lower carb intake is far better for their health than whatever marginal nutritional difference exists between grass-fed beef and grain-fed beef.
Beyond that, some things are just more expensive. Brussels sprouts here in the U.S. tend to be very expensive fresh; they're much better priced frozen. Since I live in a part of the country where local fresh produce simply isn't available for most of the year, I often get by on frozen vegetables or cabbage, which we like a lot and is almost always cheap (unless we want fancy cabbage). We eat a lot of chicken and I pass by the meat and fish packages that cost US$15-20/kg. All this kills a little variety in the diet, but we all make choices.
Again, not to lecture or "mansplain", just mentioning that there are some barriers others put up to eating keto but that they don't necessarily have to exist.