Having issue with Image quality in Photoshop

I am having a problem with image quality whenever I save from photoshop. My job requires really good quality images with small size that is less than 50kb, which is not impossible when I use 'Save for web' command, but it always comes out blurry as it shouldnt be. What I do when saving it is choose 'jpeg' as the format, choose the best quality possible that allows the file to be smaller than 50kb, 'Progressive' box ticked, but the result is not acceptable. Its been driving me sane since if my college does it, the exact same process from the exact same file, it comes out with really good quality, sharp and clean. Is there anyone experiencing the same thing? Does anyone know how to fix this? Or is this because of some settings in photoshop that I accidentally did that causes this issue?