Earlier quoted context omitted.
The economics are different because the industries are fundamentally different. Software is never "finished" the way a building is finished. More features can always be added to software. If those new features create new product lines and attract new revenue, then the software engineers' salaries are more than paying for themselves. But, this obviously carries risk, that the new thing you develop won't be worth as mu…
> Software is never "finished" Software may never be finished (in your opinion) but the budget of any customer is finite. If you keep reinvesting your revenue forever into "engineering" the product there's going to be a time where a competitor comes in with a finished product matching your customers' requirements and snatches him from you by both charging less and making a profit.
The reason why software companies grow, is because businesses demands growth.
I suppose you could build a simple, small app and leave it on "maintenance" (even then, it's going to be difficult due to crumbling infra) but real world products don't work that way.
Companies want to scale, add features and expand to various verticals. They also have to compete with other companies , there is regulations, compliance and never ending list of incoming features from sales, marketing and customers.
Elon Musk famously attempted to run Twitter "lean", and look how that ended.
Unless you are able to curb the corporate greed, you will need to grow your engineering team.