Buying Point to Point train tickets - cheaper in US before we leave or wait until we get there?

To test the walk up prices just enter tomorrow’s date as your day of travel for each pair you want to buy. You can compare an almost walk up price to your date in the future.

What Mona said. On some routes / trains, there is little or no discount to buy in advance, so best to wait and buy when there. On others, there is a big discount, but also restrictions, so up to you whether it is worth the savings to be locked in to an exact date and time. Enjoy your trip.

What website are you looking at? You can look on the official train companies websites and compare tomorrow's fares with your October dates to see the differences. Or just do the same thing on the traineline.eu website. For long distance tickets we've been able to save quite a bit of money, but we're fine with the restrictions that go with the saver fares.

I use a rail pass in Germany, and I also buy point to point tickets both way ahead of time , ie the 92 day discounted tickets plus those point to point ones usually the day before departure from the ticket machines using cash or a credit card...just depends.

"...then we can't change them at all." Very true. You've locked yourself in, sacrificed flexibility for savings. Those point to point tickets in Germany do indicate the price.

If you're looking for good pricing, consider...

Westbahn for Vienna to Salzburg has a 8€ deal for pre-purchase; Salzburg to Bamberg can be done on a Bayern Ticket day pass (€31) which you can buy at the station in Salzburg. The Bayern Ticket specifies the use of regional trains to Bamberg - figure 5.5 hours from Salzburg on the best connections - but you have a flexible travel schedule for that day.

You can shave off some time with DB saver fares between Salzburg and Bamberg but as you've discovered, your trip will be train-specific, and the Bayern Ticket will still cost less.

Less than €50 for two is pretty good. So slow travel often pays off.

If you're in a hurry to get to Bamberg and you want total flexibility then the buy-at-the station option will work but two will pay around €240 for the trip from Vienna.

The ONLY reason to buy ticket ahead of time on the web is to take advantage of any discount program might be available to you for advance purchase. And the applies if you are in Europe or the US. A bit like our US airline pricing except that it is much more straight forward and understandable. And, of course, discount tickets come with restrictions.

Remember the german rail pass is also valid for several major cities outside of Germany, like Amsterdam and Prague, but not Vienna. The mode is usually bus rather than rail.
See page two of this pdf: https://www.bahn.com/en/view/mdb/bahnintern/international/redaktion_bahn.com/pdf-datein/pdf_2018/mdb_268059_german_rail_pass_2018.pdf

Last summer, we used the German rail system. We were able to find a number of bargains which cut our costs in half. Off-peak travel is the key. Buying ahead of time cuts you off from these bargains.

Has anyone purchased their tickets ahead of time or is it just easier
to buy them at the stations?

We always buy rail tickets ahead of time for the substantial price savings. It's very easy to do. If for you travel flexibility is most important, you can buy at the station easily and pay the premium for that flexibility.

I buy some tickets (typically shorter trips) at the station but mostly purchase ahead to get the discount. The key is knowing you can reach the train you are booking. If you miss the train, you may be left buying a new ticket at the station and wasting the price of your pre-purchased ticket.

Sometimes that isn't the case. I went to the wrong station in Paris on one trip. I didn't notice until I printed my ticket at the station kiosk. I didn't have quite enough time to get to the right station and missed my train by a minute or two. I talked to a station manager who said, just get on the next train.