This is a good question and requires looking at various socio-cultural aspects. Indians have a lot of misconceptions about Punjab, both in a positive and negative way. Bollywood has played its role in pushing the Punjabi stereotype.
For someone like me who has lived all over India, I have encountered different kinds of Punjabis:
- Post partition refugees from Pakistan
- Punjabis who have never lived in Punjab (typical Bombay Punjabis, some of whom could be refugees too)
- Punjabis whose parents lived in Punjab but children grew up elsewhere
- Punjabis who live in Punjab
They all differ in their temperament. But I don't want to get into that.
It's the category 4 Punjabis who are relevant to the answer here. For me who is not very well versed with economic data, it is difficult to say if the Green Revolution caused the prosperity in Indian Punjab or is it Punjab which was the ideal setting for the Green Revolution to start with. Perhaps it is a bit of both. Punjab has had a decent canal system since British times. The hard working stereotype applies more to category 1 and 2 Punjabis. Farmers in all states in India are hard working, so that part was not unique to Punjab.
I think despite the differences in the 4 categories I described above, there is a common thread that runs through all Punjabis, and that is their willingness to spend on things they like. This pushes them to work hard for it and generally creates a consumer culture that is good for the economy. More importantly this mindset applies in rural areas as well, so we see similar spending patterns there. However the image of Punjab as a happy agrarian role model is partly due the absence of large scale industries (except some food processing), due to which it is the farmer and not the businessman which dominates the cultural references. Having said that, Indian Punjab does not lack urban areas. Patiala, Ludhiana, Jalandhar, Bathinda are decently sized cities. Indian Punjab is after all not that big geographically.
Barring the cow belt (also called the BIMARU states), the conditions in rural India are not that bad actually and Punjab is not significantly better. Punjab is certainly not better than rural South India in living standards. I think where Punjab fares better in is how the poorest live, at least as far as diet goes. North Indians in general love their milk and milk products, and would rather spend a larger portion of their income on food, as compared to other things.
Today's Indian Punjab is actually not a role model in any sense as far as policy making is concerned. When examples of progressive states are given, it is almost always the southern states and Maharashtra / Goa, or at best Rajasthan from North India. Punjab is actually considered a state resting on past laurels where the youth are struggling with drug addiction and forever dreaming of migrating to gora lands.