and now, you have v3. The bundling will grow exponentially!
It’s quadratic, not exponential. For N versions, you have prices:
N * (N + 1) / 2
2015 - you sold v1 for $5.00
2017 - you start selling v2.
You sell v1 for $5.00 but in the description tell everyone not to buy it.
You sell v2 for $5.00 but direct people who have already bought v1 to buy the bundle of v1 and v2 that you price at $8. Anyone who has already bought v1 can buy the bundle for $3.