Three weeks, about 1,900 kilometres, no aircraft. Buses, two trains, one boat, and a great deal of sitting still while the landscape did the work.
What it costs you
Time, obviously, and more than the schedules suggest — the loss is not the journey, it is the buffer days you need around every uncertain connection. A flight that takes ninety minutes took four days. Over three weeks that adds up to about a week of pure transit.
It is also not cheaper. Six overland legs with a night in a guesthouse either side of the awkward ones came to more than the flight would have. Anyone telling you overland travel saves money is comparing the ticket prices and ignoring the beds.
What it gives you
Continuity. This is the only honest answer and it sounds thin until you have felt it. Flying deletes the space between two places; you step into a room in one city and out of a room in another. Overland, the change is gradual and you watch it happen — the architecture shifting, the food changing ingredient by ingredient, the language sliding through two or three intermediate forms.
You arrive understanding where you are in relation to where you were. That is a small thing and it is the entire reason I do it.
Would I do it for a two-week holiday
No. Absolutely not. This works because my time is elastic and my deadlines are mine. If you have fourteen days and a return flight, spending five of them on buses to feel philosophically consistent is a bad trade, and I would fly.