For JSA tours, the main operators are Cosmojin and Koridoor. They all follow the exact same itinerary since the JSA is government controlled and has strict rules. They simply just depart at different times during the day and also do different things before or after the JSA part. The price should all be the same, around 90$. Anything that's not 90$ doesn't include the JSA. They do have times throughout the day, including afternoon departures, but it varies based on the calendar/day. Do book ahead as it sells out in advance.
Any other companies you find should be the exact same price as Cosmojin and Koridoor. Websites like Korea Travel Easy and Trazy all sell tours for this and other things, and use the same operators. They are just different local companies doing the same thing.