Anisotropic S-bahn.

Euclidean space is isotropic, as we all know. S-bahn network is a bit different story. Let’s assume $ is a metric. Then cost of S-bahn transport from point A to point B would often be different than cost of going back from point B to point A.
For example:

I have a monthly pass that lets me travel free in zones 1-4. Imagine I am standing on a platform at Grub, which is located in zone 5, two train stops away from a border with zone 4. If I would like to travel home (Ostbahnhof, zone 1) from there, I would need to buy a “kurzstrecke” ticket which costs me 1.20E, and is valid until Feldkirchen. I can also save few cents if I use one stripe of “striefenkarte” that would also work till Feldrkirchen. As Feldkirchen is in Zone 4, I can continue the journey with monthly pass.
But what if I want to take the same train back and go in the opposite direction, from Ostbahnhof to Grub? If I stamp my “kurzstrecke” ticket or use one stripe of “strifenkarte” at Ostbahnhof, that would also cover two train stops, just from Ostbahnhof to Berg Am Laim. And I will pay a 40E fine + ticket if checked between Feldkirchen and Grub. So what do I do? I’ll have to stamp 3 stripes, or buy a single trip ticket for 8 zones.

There is of course a workaround. I can buy a “kurzstrecke” ticket at ostbahnhof, get off the train at Feldkirchen, stamp it quickly and rush back to the train. That would work if I am fast and lucky, other ways I’ll have to wait 20 minutes for a next train. It also helps that Feldkirchen belongs to both zones 4 and 5, other ways the trick would work for “kurzstrecke” but not for “streifenkarte”. Wikitravel article about Munich transport actually recommends similar trick for cheaper transport from the airport.

Upd: Thanks irre, it should be rings not zones. A zone is 4 rings.