Train Passes

Unfortunately the answer is not a black and white yes or no. At one time a rail pass was a "no brainer" good deal but advance purchase discounts,other promotional deals, and seat reservation fees it becomes more questionable. You need to lay out your entire travel schedule and price it out using the German train site and then compare the total price with the price of the rail pass. That is the only way to know if a pass is cost effective.

With only 4 ICE connections in 4 weeks a train pass makes no sense.

If you know the exact dates and times of travel you can book saver offers incl. city ticket from address to address in advance. On arrival from an airport you can also book flex tickets to get the next available train on a day or the day after.

Those saver tickets mentioned above are available from some two months from the travelling date at Bahn.de (the German national railways). Mind that these tickets are train specific, and non-refundable.
For this reason they are not recommendable for your first trip from Frankfurt to Bonn. Any delay with your flight or a longer than expected handling at the airport will make a saver ticket worthless.There are, however, cheaper tickets available by using regional transport instead of ICE/IC trains. Tick the box »only local transport« to see these alternatives.

For the Frankfurt-Bonn trip you cold check whether your airline participates in DB's Rail&Fly programm. A fully flexible R&F ticket would be €36. Or you could take the 30 min slower train via Mainz (follows from Main the left bank of the Rhine). A flexible ticket is €42 or €44, depending of the typ of train. For the other trips I'd book train specific saver fare tickets asap (booking opens 6 months out!).

A German Rail Pass for 4 days of travel within a one-month window (such as Sept 15 - Oct 14) costs only $185 per person in 2nd class. That's $46/day, versus the €30 advance-discount rate that you might find for Bonn-Munich if you book now. The pass is the more convenient option, if you're not ready to lock in dates and times. Will you not need any other train travel during 4 weeks? An extra day on the pass costs only $12 per person, for instance.

The 4-day German Rail Twin pass (flexi version, 4 travel days within a 30-day period) covers two adults for €314 ($350) at DB (German Railways.)

You could use Day 1 of your pass to travel from FRA airport to Bonn; if your flight is late, there are no negative consequences like you'd have with a saver fare ticket - whatever time you reach the airport train station, you just hop on the next train to Bonn.

Will you be staying in Munich for your final night? If so you'll need to get the train to MUC airport the next morning, right? The 5-day rail pass costs just €21 more (€335 total.)

So buying the pass from DB... for those 5 trips x 2 adults = 10 trips, you will average €33.50/trip each - or US $37.30. And in contrast with those pre-purchased saver tickets (at unknown prices...) the German Rail pass means that...

• ...you only have to buy ONE travel document
• ...you don't have to pre-purchase things in a rush (like you would with the saver fare in order to get the best possible price)
• ...you have schedule flexibility in case you want or need to change your travel times
• ...you can insert a stopover or a detour (like Nuremberg, or Cologne, or...?) on the way to your destinations
• ...you avoid the possible forfeiture of your DAY 1 saver fare ticket.
  

The GR pass sounds like a good bargain to me!

I would never buy a rail pass for only 4 days.

If it were ten or 15 days in a 2 month period, then I buy the 2nd class Senior Global Pass since I do night train options and zig zag traveling.

You aren't traveling extensive enough and the duration is too short.

I'm with Russ. I've purchased short term German Rail Passes, they are a good value if you want ease and flexibility without being locked in to a specific train. I was actually considering purchasing a twin 3 day pass to go to Berlin and day trip to Duessdorf just for some Japanese food!

In total the tickets are between 70 and 80 Euro cheaper than the pass incl. 1 Flex ticket at day of arrival. A lot of money especially on that base. Question is how much you want to pay on-top for convenience and permanent flexibility.

Btw: For Frankfurt - Bonn you may better take the direct IC train along river Rhine through scenic mid Rhine Valley which arrives at Bonn main station - the ICE arrives at Siegburg. From there you would travel to Bonn by tram - and you wanted to take a taxi out of Bonn main station. If you take the taxi from Siegburg it will be much more expensive to center of Bonn.

In total the tickets are between 70 and 80 Euro cheaper than the pass
incl. 1 Flex ticket at day of arrival.

Mark, I do not doubt that you were able to find specific prices for arbitrary travel dates - but without the specific travel dates and time of travel that the OP will actually use, the total costs of p2p tickets you refer to are hypothetical. And of course, any specific prices you found are valid for the moment you found them, not necessarily for the actual moment when tickets are purchased by the OP.

Below are a couple of additional rail pass advantages that I failed to mention previously...

• On the days you use it, the GRP is valid all day long. So you can ADD any train journeys you like that same day. For example, after your Bonn > Munich journey, you could drop your bags and ride the S-Bahn out to Herrsching and back for no additional charge; similarly, after your Day 1 trip to Bonn, you could hop on a train to Cologne and back, if you wished.

• Should you happen to board the wrong train - say you board a northbound train in Bonn instead of a southbound train, for example - your error is automatically forgiven if you have a rail pass. A similar error with a p2p ticket could result in a large fine.

And if you happen to miss a ticketed train ride like Munich-Bonn, a new ticket tends to cost either €117 or €153 per person, depending on the change points (plenty of departures at either rate).