Car/Bus Service for 10 people from Oberhaching to Neuschwanstein Castle or just take train?

Because the rail lines in Bavaria basically branch out from Munich, you will probably have to go back through Munich to get from Oberhaching to Füssen, so it will be slower than driving directly. However, for 10 people, 2 5-person Bayern-Ticket, at 49€ each, or 98€ for all 10 of you (less than 10€ per person), is undoubtedly the lest expensive way to go.

The Flixbus web site offers an individual small bus for €600vv. You might be better of with a local bus company but not dramatically - certainly not under €500.

With Bayern Tickets, you can leave from Deisenhofen S-Bahn station at 9:10 am and be at Neuschwanstein by 12:20. If you want an earlier start at 8:10, along the Bayern Tickets, buy 2 MVV XXL group day tickets for 16.10 EUR each. Those tickets will be good to Munich Pasing on the S-3. There you change to the regional train to Fuessen leaving at 9:00 am, so the Bayern Tickets will now be valid for the rest of the day. After changing to the bus at Fuessen, you will be at Neuschwanstein by 11:13.

Those MVV XXL group day tickets can also be used to go into Munich for the Wiesn'. Just remember that all 5 of a group have to travel together all the time. If people want to go back early, they would have to buy individual tickets to go back to Deisenhofen (Oberhaching).

Thanks for the information everyone! I suppose with the group tickets it is cheaper than a "normal" train pass. I am still worried about the time it takes since we are limited. I did get a quote from a company called GeldHauser and would like a second quote just to compare. I'd like to deal with a company directly and not a third party - so if anyone has one to contact I would love that! Thank you!

Not sure what a "normal" train pass is that you are referring to. Eurail Pass? German Rail Pass? Most assuredly, the Bayern Tickets are the lowest cost way for a small group to travel in the region.