From 1992, the UAE has offered a "marriage fund" to address what it describes as the
problem of increasing number of spinsters as well as the reluctance of UAE men to marry national women.
According to an essay [PDF] published by the Population Reference Bureau, these trends were due to increasing dowries
As in other oil-rich Gulf countries, an increasing number of families in the United Arab Emirates (UAE) received a boost in their disposable income during the 1970s from that decade’s oil boom. As a result, lavish wedding receptions and expensive gifts to brides in the UAE became more and more customary. But the rise in marriage costs (which are traditionally borne by the groom and his family) prompted many UAE men to go outside the country to marry foreign wives and bring them back to the Emirates. The phenomenon of UAE men marrying non-nationals led to the creation of two visible groups with which the society as a whole was not at ease: single UAE women with little prospect of marriage, and children of mixed marriages being brought up by mothers not much in tune with UAE traditions and culture.
These grants have a value of Dh 70,000 - approximately US$19,000, and come with various conditions.
According to a citizen journalist article published by The Times of India in 2013 (so post-revolution), a similar system operates in Libya:
The marriage grant fund's goal is to enlighten [sic] the economic burden of marriage on young grooms and to encourage UAE men to marry UAE women. Similar marriage grants also exist in Saudi Arabia, Bahrain, Qatar and Libya by the respective governments.
The Libyan National Transitional Council established such a fund in 2012. I can't find any other references to a Gaddafi-era fund but the above suggests that the existence of one would not be out of order.
The source quotes Libya's per-capita GDP at US$95,000, which is clearly some sort of exaggeration. So, in short: many nearby countries, including post-revolution Libya, offered marriage funds defraying what would otherwise be the cost of a dowry. It is not unreasonable to expect that Gaddafi-era Libya offered something similar. The US$90,000 figure is probably an exaggeration.