If people actually gave, say, 5% of their income on average to the Church, then the Church's ministries to the poor, widowed, orphaned, and destitute would be greatly magnified. However, I'll venture a guess that many (I won't say "most" or anything like that) give 1% or less to charity.
2007 approx. median household income: $50,000 (thank you, wikipedia: http://en.wikipedia.org/wiki/Household_income_in_the_United_States).
If 0.5% of US homes are Orthodox, then that's 560,000 Orthodox homes. If each home gave 5% of their income to the Church, the Churches would receive $1,400,000,000.00 in contributions, and I'll venture to bet that at most
30% of that number ($420,000,000) would be used for administration (for 2,000 parishes + dozens of other organizations including diocesan administration, web services, theological schools, and the like; $200,000 per organization). That leaves nearly $1,000,000,000 (one billion, for those who don't like lots of zeroes) for charity. Think about that. 5%. Not a 10% tithe; only half
(Oh, my speculation about 1% above would equal, with the demographic info, about $280,000,000, which makes sense considering how many parishes don't have a full-time priest, and how many organizations depend
on festivals and other fundraisers to pay the bills.)