A few things that will reduce Photoshop file size:
– Save without backwards compatibility.
– Select all and crop. This will get rid of most of the things outside the actual image area (smart objects being an exception).
– If you still want to use “save as”, try flattening image before saving as.
Depending on the smart object content you have, rasterizing them may either increase or decrease the file size.
—
What is the problem with “save for web?” It produces a smaller file than direct “save as”. More importantly, there is an option “none” for metadata in that dialog.