Price started Stage 9 just 1:06s off the overall lead and was vying for the lead of the special when he went down, 155km in.
The broken collarbone was announced by the factory KTM squad after the conclusion of the Neom loop stage.
The Briton explained how he had a crash of his own after Price's fall.
“Obviously, it's been a pretty rough day today,” said Sunderland.
“I started off strong, and was making good progress, handling the tricky navigation well.
“Then I came across Toby lying in the riverbed with Brabec already stopped with him.
“I helped there ‘til the helicopter arrived then set off again and tried to get back into a good rhythm.
“Around 100 kilometres or so after that, I was opening up for the group I was with and was looking down at the roadbook, hit a rock and was sent over the handlebars.
“It was quite a big crash, quite a big impact, and luckily I wasn't too badly hurt.
“But, I damaged the road book tower on the bike had no navigation from then on.
“I managed to reach the finish by following others but that's always hard.
“A really tough day for the team, but this is Dakar and it's always a challenge. We'll regroup and do our best again tomorrow.”
For Price, the retirement is his second in seven Dakar starts to date, after suffering a badly broken leg in 2017.
Australian rookie Daniel Sanders, also a factory KTM rider, holds sixth with three stages remaining.