That process is now slightly decelerated but unfortunately we do not have alternate system to bring them to market in a fast pace so vegetables are there but they are not available in the market in that big amount as brought by the selfish traders earlier.
Another possible reason could be overall decrease in production and due to demand supply mismatch prices will rise.
Thoughts exchanged is knowledge gained.
So, there seems to be a major issue other than supply and demand imbalance, I think time plays a crucial role, it's the timing of the crop, untimely rains damaging crops,interrupting land transport, poor infrastructure to shift these vegetables in time before they get spoiled etc. There could also be a case of middlemen hoarding items, some states are known for their onion hoarding cartels.