Illustrator currently increases the size of a file by 400% when using the "Export As" option and choosing to save at 300ppi resolution instead of 72ppi resolution. We tried several times exporting as PNG for an Artboard that was 5000px wide but the program saved the file at 20000px wide because we chose to save at 300ppi resolution. We contacted support and they stated that this was a "feature" of the application and cannot be changed.