I'm not sure if you realise this, but the UAI/ATAR cutoff listed in the book is from the previous year. Just because the cutoff for degree X was 90 in one year doesn't mean it'll be 90 in the year you receive your ATAR. If a lot more students apply that year, it may become 99 instead, or if a less students apply in that year, the ATAR cutoff may be 75 or lower. Similar effects will occur if the uni decided to change the amount of students they are too accept.
In other words, for most courses in most unis, they look at all the students who apply and accept them in order from highest ATAR to lowest ATAR. If degree X accepts 50 students, and the ATAR of the 50th student is 98, then the ATAR cutoff is 98.
In other words, choose your degree not based on the cutoff, not (entirely) based on the salaries, but based on how much you think you'll enjoy it (and whether you're capable of the work involved in this degree). Choose your degrees in order of preference (but be sure to choose a degree with a very low cutoff (as cutoffs will generally be similar from year to year) as your final preference just incase you don't meet the requirements for any of the others. Generally you should know the ATAR you'll receive, within 5 or 10 points at least.