First few corrections for you. All the money spent on Deep Space Research does not disappear in thin air. It is used to pay salaries of scientists, technicians, labourers, local businesses. Most of them are not exactly those who can leave India and go to Europe. In such massive project, behind one engineer or scientists, there is an army of workmen to build infra and assemble machines. Simply put it does employ quite a few folks. So whatever number you have for those driving taxi, they have to be adjusted over and above it. I am not sure if the gain is going to be substantial.
Secondly, it also encourages more people to pursue higher education in technology, science, engineering and at-least workmanship. And higher education is almost always associated with better employment outcomes.
Lastly, you didn't address the most important argument : If instead of deep space program worth 100 million dollar a year, religious institutes which are earning in 10s or 100s of billion dollars per year for doing nothing better than some prayers are targetted and their revenue and profits and gold assets are tapped into providing employment, you will have really better outcomes.