BLR Airport Railway

The high-speed rail link project to BLR airport was cancelled due to elevated costs. Currently, an extension of the Gottigere-Nagavara metro line to the airport is planned. Isn’t this quite expensive as well? Why not just upgrade the Chikkaballapur railway line an build a short airport branch (4km) from the existing line that is passing next to the airport?

BLR Airport Railway Mini Map