There are reasons why BYD asks to be paid in front.
Because India is well known for not willingly to pay for the bus in the first place, I think BYD know this from their past experience.
In other country, everything India buy, it's always far more expensive because everyone knows in the end, India will not pay by creating any reasons not to pay, like accusing for defective product, etc.
So, by increasing the price foreign country will get profit as it should be whatever in the end India government is going to pay it full or not.
India mentality is thinking that any transaction is like transaction in the wet market.
If the seller is not losing money, then the buyer is not satisfied, not winning, not smart.
For Indian politicians, BYD stand for paying first is a great insult and a loss in India side.
This kind of mentality and combine with the geopolitical rivalry and USA media propaganda, making a trouble to China is a kind of heroic thing.
In BRICS, India is the least of having solidarity, it's a pain in the @ss.
Sabotaging and backstabbing the members of the group they joined, while the rest of the members are working hard to make all members prosperous.
Up to today, India doesn't have any idea why China is willingly to invest in India, to give cheap loan for infrastructure development, to connect India to the rest of the world, building factories in India instead of other countries.