The phrase "a modest sum of" is correct and usable in written English.
It can be used when referring to a small or reasonable amount of money or resources.
Example: "After careful consideration, we decided to invest a modest sum of $5,000 into the new project."
Alternatives: "a small amount of" or "a reasonable sum of".
Lawmakers who opt to live in this housing could be charged a modest sum of $500 a month.
At the start of the school year, you contribute a modest sum of money.
By way of indemnity, he demanded a modest sum of money.
A modest sum of €230m could generate €4.6 billion worth of projects, says the Commission.
He found out from Bob's lawyer that a modest sum of money could come to them from the sale of some property in Florida that Bob owned jointly with Howard Weller.
Years later, Mr. Adams relished joining his college pals in Atlanta, where they would throw a modest sum of money into a pot and select their fantasy football teams for a season-long competition.
The official biennale budget was less than $1 million, a modest sum for an exhibition of nearly 300 works.
The dating company declined to reveal how much the game makers were paying it in addition to providing games, saying only that it was a modest sum to defray the cost of events, and Ms. Nathanson, without giving a sum, described the cost as "dirt cheap".
The total aid from developed countries is about $100 billion a year, a modest sum in light of developing countries' needs.
It also anticipates program cuts that, by 2004-5, will be worth more than $200 million a year -- a modest sum in light of the deficit and Mr. Pataki's history of trying to make much deeper cuts in health care expenses.
The federal government has put aside a relatively modest sum of $1.4m over four years to create an injury compensation scheme for parliamentarians who might get injured while in the Big House or undertaking their duties in the electorate.
