$280 billion in what type of investment? Iran doesn't agree to India building ammonia ppant in Iran as Iran wants some control of the assets! Iran has very little opportunity to invest for anyone unless Iran is under sanctions and desperate for some foreign exchange that they will agree to sell some of their oil and gas fields on lease. Even then, $280 billion investment is suspicious. Iran has is own power generation facilities and road construction facilities due to abundant oil and gas and consequent development of infrastructure and availability of raw material in these fields.
Investment in oil and gas fields isn't that high and Iran is also unlikely to lease most of its large oil & gas fields to other countries. So, where is the investment going?