From news article:

The IMF estimated Gaza's 2009 gross domestic product (GDP) growth at 12 percent, an impressive number. According to a September 2010 IMF report, the total Gazan and West Bank GDP was $7 billion, while the gap in per capita income between the two areas was 48 percent; this data, combined with other relevant statistics, implies that Gaza's per capita GDP was around $1,400, much of which derives from payments by the PA. Transfers and remittances added 50 percent more income, implying that average total per capita income was, in fact, $2,100. Yet much of this income does not represent productive economic activities, and unemployment remains high -- probably around a third of the workforce.

One must also take into account the considerable trade conducted via the more than 800 tunnels into Egypt. Based on fragmentary evidence, this trade likely peaked at around $600-850 million per year. Much attention has already been devoted to the goods smuggled into Gaza, such as fuel and cement. Less well understood is the fact that, in exchange for these goods, cash has been steadily exported out of Gaza through the tunnels, at a rate of roughly $750 million per year. Cash is also flowing out of Gaza -- through the tunnels and via bank transfers -- to safe havens in Persian Gulf countries and Europe. The new wealthy class -- many associated with Hamas -- as well as established capital owners are concerned about keeping their money inside Gaza, preferring to move it abroad. And even with huge sums flowing out of the territory, there is still more cash than opportunities to invest it. In February 2009, for example, Gaza banks actually turned to Israel's Central Bank with an odd request: to deposit excess cash reserves in Israel.

Where does all this cash come from? Many assume that substantial sums
have been entering Gaza via the tunnels since 2008, but this can be only partially confirmed. Instead, the cash inflow seems to come primarily through banks. According to Palestinian banking officials, an average of $2 billion per year has been transferred into Gaza via the Palestinian banking system since Hamas's June 2007 military takeover. The PA alone wires an estimated $1.2 billion per year into Gaza banks, much of it as pensions and salaries for the 77,000 employees kept on the payroll even though they are not working. In fact, this estimate may be conservative; according to PA prime minister Salam Fayad, 54 percent of the PA's $3.17 billion 2010 budget went to Gaza. Most of that figure appears to be salaries, although it also covers what the PA pays directly for electricity, fuel, and water provided to Gaza by Israeli firms.

In addition, the UN Relief and Works Agency annually transfers about $200 million in cash to Gaza, along with $250 million per year worth of goods, grains, and fuel. Cash is also transferred into Gaza by the 160 nongovernmental organizations operating there, by international organizations such as the World Bank, and by foreign government aid organizations, although much of what they spend arrives in the form of goods shipped via Israel.

Hamas Resources

Hamas officials consistently refuse to disclose budgetary details or any other information regarding their sources of income. One official, Jamal Nasser, claimed that the group derives only $60 million per year from fees and taxes, with the rest coming from gifts and foreign aid. That does not appear to be the case, however. According to Israeli military intelligence, Iranian subsidies to Hamas total around $100 million annually, or less than 20 percent of the group's proclaimed budget, stated to be $540 million in 2010. Iranian funds are directed mostly toward the Hamas Political Bureau in Damascus, primarily for weapons purchases and shipments, rather than toward Gaza. PA president Mahmoud Abbas has offered a much higher estimate, claiming that Iranian aid is approximately $250-500 million, but little evidence supports his figure.

Hamas likely raises as much as $250 million annually via taxes. The group has imposed all sorts of new fees and taxes, such as charging three Israeli new shekels (NIS) on every pack of cigarettes (which may generate around $80 million annually) and an NIS 1,400 auto registration fee (which may generate an additional $25 million based on estimates of 60,000 registered cars in Gaza). Hamas also regulates many types of businesses -- from street vendors to Gaza's twenty money-changing companies -- requiring them to pay license fees. In addition, taxes are collected on "luxury" goods coming from Israel, and even on motorcycles and carts.

Hamas also takes a hefty cut from the Egyptian tunnel trade, imposing high "customs" duties and a daily fee on local tunnel contractors. Such trade has been dramatically reduced since June 2010, when Israel quadrupled the number of trucks permitted to bring goods to Gaza through legal terminals. To replace lost tunnel income, Hamas is reportedly taking advantage of the relative drop in prices on goods arriving via official Israeli channels, imposing new taxes on various items. For example, from early July to September 20, 2010, the group barred the importation of new cars from Israel until the taxation issues were resolved.