The phrase "a hefty sum of" is correct and usable in written English.
It can be used when referring to a large amount of money or a significant quantity of something.
Example: "After selling the property, she received a hefty sum of money that allowed her to travel the world."
Alternatives: "a large amount of" or "a significant sum of".
New Blues: McLeish's savvy signings *Roger Johnson: The defender was prised away from Cardiff City for a hefty sum of £5m but has been outstanding.
But Arthur was given a hefty sum of money by his father, made more as an art dealer, and became richer still when he married Hortense Mitchell, the daughter of a Chicago banking magnate.
"Without a hint of irony, one of the leading lights of the supporter-ownership movement was offered a hefty sum of a supporter-owned football club's money to snoop on the internet activity of co-owners of that very club, once the poster boys and girls of the supporter-ownership movement.
One day, he was an honorable man victimized by the establishment; the next, he was, in the words of The Daily Mail (which had offered a hefty sum of its own), an isolated "outcast," reviled by all (except The Daily Mirror).
The short-term commitment gives him a chance to earn a longer and more lucrative deal next off-season, but it is a hefty sum of money for a soon-to-be 34-year-old who has not played since accidentally shooting himself in the leg in November 2008.
That makes the total raised for Ev Williams' Medium a hefty sum of $82 million.
It drains a hefty sum out of your bank account on a regular basis.
Australians spent AU$500m£24242) on bottled water in 2008, a hefty sum for a country of just under 22 million people.
If that happened, he could invoke his right to leave and collect two years' worth of compensation, a hefty sum for a man who took home $16 million in salary and bonus in 2003.
It seems like a hefty sum to throw behind a Windows Phone of all things, and it's reportedly even more than the carrier was thought to have spent on pushing the iPhone.
SLOC expects the budget for 2002 to be well over $1 billion: far less than Nagano spent, but still a hefty sum for a state with an acute dislike of taxation.
