I hope he likes the Orijen.
Hopefully it was the bag of treats that he ate that caused his vomitting. If he continues to be sick please take him to your vet asap.
The reason the Orijen Red Meat is more expensive is because it's new. The chicken formula is the least expensive one they have. Champion Pet Foods also makes Acana Provincial and it is grain free as well. They have a chicken formula, a fish formula and a lamb formula and they are all a little cheaper than Orijen as the meat protein content is lower but the ingredients are just as good.