I encourage you to take a look at this picture by Grant Gunderson:
That is a professional shot, and it still looks professional when it is sized to 25K. If a picture can look that good at 25k, then 30k as a limit should be more than acceptable.
i know there is a way to do that in photoshop with the save for web setting if i remember, but i dont really know how to use that, someone should post directions or something.
Go to file, save for web. Select JPG and set the picture quality to 50-60%. Save it! That's about all there is to it.. you can click all the other options on and off to see if you can make it even smaller, but I know nothing about them.