(I think the advantage this approach has over the one you've suggested is that the product is always capable of making money even from the very beginning, just on a smaller scale at first. I think this is a critical feedback mechanism so that folks know whether what they're developing is actually useful to folks.)
Come out to Microconf sometime. You can meet ~300 nobodies all at once!
I would claim there is still a large chunk of areas that have very poor service from the software field and would find tremendous value of a trivial software product that is just applied correctly. So it's more about service design rather than hightech, if one is just looking to make a profit.
As an example...
Building and construction is still in infancy as what it comes to utilizing digital technology. The field is fragmented with long subcontractor chains. The digitalization that happened in e.g. car manufacturing is not yet complete. The field is dominated with clunky, expensive cad packages which, while some may be eatabslished standards, are never the less decades old piles of legacy software. Most of the data is still transmitted between parties in paper drawings.