The Spain international will spend the 2019/20 season on loan in north London having been deemed surplus to requirements at Real Madrid.
But Starsport understands Los Blancos have snubbed the chance to subsidise his £60,000 a week wages.
In addition, Arsenal appear to be paying a £12m loan fee.
Ceballos has bagged the No.8 shirt and could make his debut in the Emirates Cup this Sunday against Lyon.
“Dani Ceballos could cost Arsenal £15m ”
Gunners boss Unai Emery said: “We’re excited to see Dani join us.
“He is a talented player with big technical ability, creativity and precision.”
Arsenal have only limited funds this summer – but Real won’t contribute to Ceballos’ pay packet.
The Sun say the total deal will cost £15m. Once his wages are taken into account – around £3m a year – that suggests Arsenal have rubber stamped a £12m loan fee.
It’s claimed the Gunners are not tied to a compulsory purchase option at the end of his temporary stint.
William Saliba is another fresh face today, but the exciting defender will return to Saint-Etienne for the 2019/20 season.
Arsenal have handed over £27m to complete the deal after fending off interest from Tottenham.
“We’re delighted William is joining us,” Emery said.
“Many teams wanted him but he decided he wanted to come to us and be part of our future.”
Saliba says Arsenal historic french connection was a major draw.
“The history, the badge… since I was little, I’ve been watching Arsenal play,” he explained.
“There are a lot of French players who have come through here. So that really helped me to make my mind up.
“This is the biggest club in England for me.”