"They are there to represent us all, to form laws, to send young people to war. It is not an easy thing to do. We want to have good people doing the job and they need to be paid fairly.
"Now, that's not paid in excess but it's not being paid a miserly amount either ...
"It's our job to reach the judgment of what the right amount is.
"There are lots and lots of professionals in public life and in the private sector who earn a lot more than that - so it is not an excessive amount of money at all."
MPs are already due a 1% increase to £67,731 next April, and under Ipsa's plan it will rise again a month later to £74,000.
The watchdog will conduct a further review of the pay rise after the election but Mr Boo made clear its conclusions were unlikely to shift, saying previous uncertainty had allowed for another dip in the economy.
"As of now, September, it doesn't look like there is any major economic factor that would change the determination that we reached in 2013," he added.
"We have gone through the process in a really rigorous way. It is not an arbitrary figure that we have come up with."
Ipsa was set up in the wake of the Parliamentary expenses scandal of 2009, when it emerged several MPs had abused the system to get more public money, attempting to use it for unnecessary and sometimes bizarre luxuries that famously included a 5ft duck house.
The House of Commons could refuse the latest pay rise but Mr Boo - whose own £120,000 salary is £10,000 more than that of his predecessor - said it would not be right for Parliament to take back responsibility for setting their own pay.
The increase comes too late for the Africa minister, Mark Simmonds, who announced he was resigning as an MP last month because of the "intolerable" pressure on his family life caused by pay and expenses he found insufficient.
Married with three school-age children, Ipsa said Mr Simmonds would have been eligible to claim just over £28,000 a year to rent a family home in London.
He would also have been able to claim 30 return journeys a year from the capital to his Lincolnshire constituency for each member of his family.
More than 57,000 people signed a petition against the pay increase ahead of Ipsa's decision.
The accompanying letter to the Government said: "At a time when the country is in deep financial crisis, the ordinary working people of this country are still losing their jobs, have been and still are suffering wage freezes while living costs are spiralling...is it right for MP's to get any pay rise?
"Whatever happened to 'we're all in this together'?"
- Independent
