Minyan of resentment

In a place a little far from home, they were interested in a minyan
On Saturday
They asked someone to organize a minyan for a fee of 50 NIS per head for several Shabbats.
The organizer went, gathered friends, called, coordinated, checked that there was a minyan, a man called the prayer time, etc.
And he told the participants, "I receive 50 NIS for each person who prays and I only give you 40. The difference is my salary."
Believed and accepted
They happily came Shabbat after Shabbat for 40 NIS, even though they knew that the organizer was 'earning' 10 NIS for their trouble.
Is it now within the realm of God's grace?
Do they at least have a grudge against him?