Short answer: a lot.How many bloody Princes are there?
https://www.lrb.co.uk/v39/n17/malise-ruthven/the-saudi-trillionsThe kingdom has more trivial money worries too. The Al Saud are a royal family like no other: there are thousands of them, descending from the 22 wives Ibn Saud had while technically observing the Sharia requirement of four wives – max – at any one time. He was ‘father to the nation’ in more than a metaphorical sense. In the context of a tribal society, these prudential intermarriages had the benefit of binding together a number of different groups at a time when Ibn Saud was merely the head of a coalition of tribes who founded the modern kingdom of Saudi Arabia in 1932 after he invaded the Hejaz, with its holy cities, Mecca and Medina. The trouble, presently, is that his descendants all expect their emoluments. The scale of this burden can be gauged from a classified cable sent by Wyche Fowler, then US ambassador to Saudi Arabia, to his government in November 1996, exposed by WikiLeaks, in which he reports that members of the Al Saud family receive stipends ranging from $270,000 a month for more senior princes to $8000 ‘for the lowliest member of the most remote branch of the family’. The system is calibrated by generation, with surviving sons and daughters of Ibn Saud receiving between $200,000 and $270,000, grandchildren around $27,000, great-grandchildren around $13,000 and great-great-grandchildren the minimum $8000 per month. According to the US embassy’s calculations, in 1996 the budget for around sixty surviving sons and daughters, 420 grandchildren, 2900 great-grandchildren and ‘probably only about 2000 great-great-grandchildren at this point’ amounted to more than $2 billion, with the stipends providing ‘a substantial incentive for royals to procreate’ since – in addition to bonuses received on marriage for palace construction – a royal stipend begins at birth. One minor prince, according to a Saudi source, had persuaded a community college in the state of Oregon to enrol him even though he had no intention of attending classes: his principal goal in life was to have more children so he could increase his monthly allowance.
Well if Saudi wants to attack Lebanon then Israel will most probably get involved too. Saudi can only use it's air force if they want to attack Lebanon. Except if they send their proxyIran v Saudi even before Trump or Netanyahu can get their hands on that action.