I don't know if $45B is a line item to them, but to give you a sense of scale of how much money the Saudis have, Aramco had a net income of about $34B in the first half of 2017 [0].
$34B is a lot in company scales but not a lot when it is the vast majority of a government budget used to sustain a very plush lifestyle for millions of people.
Saudi has been running huge deficits and have had to dig into their reserves to the tune of hundreds of billions of dollars to sustain their spending.
In the first five months of '15 they had to draw $65B from reserves just to meet costs[0]
They've introduced a new VAT, excise on fuel, cut health and education spending etc. to prevent the house of cards from collapsing[1].
Further to that point, Saudi Arabia's population is expanding very rapidly, putting immense strain on those limited resources (which have to be used to continually pacify the population).
Unlike (almost) every other business on earth where you have to do work and compete with peers to make a profit on your efforts, all the value of oil is sitting in the ground underneath them. Oil wealth is just luck of being born on top of the right geology.
And being part of an extremist tribe who were useful to the Brits/Americans versus the Ottomans in World War 1, who then continued to provide a “stable source” of oil. Stable because they stamped out any sort of democracy or society with freedoms that would allow anyone to object to their arrangements with the West, in exchange for one family of the tribe to become extremely wealthy.
Saudi has been running huge deficits and have had to dig into their reserves to the tune of hundreds of billions of dollars to sustain their spending.
In the first five months of '15 they had to draw $65B from reserves just to meet costs[0]
They've introduced a new VAT, excise on fuel, cut health and education spending etc. to prevent the house of cards from collapsing[1].
[0] https://financialtribune.com/articles/world-economy/20960/sa...
[1] https://www.economist.com/middle-east-and-africa/2018/01/13/...