Evidently, IELTS general is easier than the academic version.
DIBP only requires the former, whereas many professional assessing bodies require the latter.
It might be a case of doing the academic version, and then deciding whether a second test is required for points purposes.
As people have said before, most native English speakers tend to overestimate their abilities, and end up frustrated and/or feel aggrieved that they did not ace the test.
There are people who have done double digit language tests, unsuccessfully.
Finally, if this test give me the points required to be given the privilege of being invited to apply for a visa, that could give my family a subjectively better quality of life, then "splurging" £200 would be the least of my concerns.