OBB Tickets -- Are they cheaper in advance?

There is an outfit called Westbahn that runs hourly trains between Vienna and Salzburg that are inexpensive. You can buy tickets on board the train.
There is also something called an Einfach-Raus ticket that allows a group of up to 5 people to ride regional trains all day (after 9 am weekdays, all day weekends) for one price of 36 euros.

You can check schedule and pricing options using the OBB website:
http://www.oebb.at/en/

See if your plans are compatible with the Einfach Raus tickets, low-cost regional transport ticket for 2 to 5 persons at 36€ for the whole group:
http://www.oebb.at/en/Tickets/Groups/index.jsp

Yes, OeBB offers "SparSchiene" rates which are much less than full fare. I believe that they are non-refundable and commit you to a particular train, so if you miss it you are out of luck. I just checked for a trip that is 90 days ahead (1 July) and ticket prices are posted on the OeBB website. So, for your May trip, there may be some special fares left but, since they are limited, when they sell out they're gone.

Those tickets are relatively affordable at full fare, so I would continue with your plan to buy as you go. Since these trains don't require seat assignments, they can never sell out. (If you needed longer travel, a rail pass could allow you the same flexibility in Austria, but that doesn't look like a money saver for this route, unless you need a return ride to your starting point.)

I just booked a "family" ticket for 2 adults and 3 students under 26. The trip from Villach to Hallstatt was 84 euros total. That's for July 7. As someone mentioned, the really cheap fares sell out quickly!! While I was making up my mind and getting out my credit card the price changed twice or disappeared (originally was 57 euros). But I now have my paid scannable ticket. I did this last year also and it saved me tons. However, the tickets are non-changeable and non-refundable. Worth it to me.

Barb

I found that the "Man in Seat 61" web site has some great advice on all sorts of rail travel in Europe. The Man in Seat 61 steered me to the OBB website, which is fairly easy to navigate and there is even an AP for you smart phone to plan trips. If you set up an account, any purchases will be available on your phone, however some individual tickets need to be redeemed at a ticket machine or maned ticket counter with a "collection code" that is emailed to you. I purchased a Sparscheine ticket (limited number) for a mid- May trip from Vienna to Budapest on the RailJet for 19 Euro and you can add a reserved seat for 3 Euro more (but you probably don't need it).

I've used this private railway service between Vienna Westbahnhof and Salzburg numerous times. It's very good, reasonable, efficient and no need to book tickets in advance. I usually just pay with cash or credit card once on board.

https://westbahn.at/en/ticket-shop/single-ticket/

Thanks for the info about the "SparSchiene" tickets. I guess they are the equivalent of the 'economy/super economy' tickets for the high speed/IC trains in Italy?

I assume the standard second class tickets will be the same price purchasing ahead of time or day of? I'm in the same situation as the OP, and if that is the case, I think it will be less stressful to just buy tickets as we go than attempt to reserve ahead of time.

About the westbanhof train - direct from Vienna to salzburg? Or does it have stops?

Regarding the Einfach-Raus-Ticket, I assume if the train listed is an IC train you cannot use the Einfach-Raus-Ticket?