When unpacked, it weighs about 100MB. This disk space costs roughly £0.004 for an HDD or about £0.020 for an SSD.
In exchange for these extra costs, I get to use HTML, CSS and JS on both our website and our desktop applications and they get to share the same codebase. That alone must saves me 50% of the time. The fact people might have to spend upto 3 more minutes to download my application and that it costs them 2p to install it on their SSD is minimal compared to the fact that I can have twice as many features in the same amount of time.