I don't think the choice for founders is between $50 million and a small shot at $10 billion - it's between $50 million and a near-guarantee of getting crushed.
In your example, before giving you an offer, the big software company will conduct an internal analysis to figure out how much money they'd have to spend to develop the bare-minimum featureset to prevent their customers from fleeing to your competing product, then they'll back that number off a little bit, and try to buy you out. This number will probably be significantly higher than the amount it costed you to build the thing, because for them to replicate your features, they have the added overhead, bureaucracy, and inefficiencies that come with being a megacorp.
If you accept the offer, it saves them money and time.
If you decline the offer, they'll just greenlight their internal projects and steamroll you.
In your example, before giving you an offer, the big software company will conduct an internal analysis to figure out how much money they'd have to spend to develop the bare-minimum featureset to prevent their customers from fleeing to your competing product, then they'll back that number off a little bit, and try to buy you out. This number will probably be significantly higher than the amount it costed you to build the thing, because for them to replicate your features, they have the added overhead, bureaucracy, and inefficiencies that come with being a megacorp.
If you accept the offer, it saves them money and time.
If you decline the offer, they'll just greenlight their internal projects and steamroll you.