You should be able to save your two problem image to the size files you want using save for web if you reduce the image pixel size by some precent and use a low quality setting.  How well an image will compress depends a lot on its content if the image is complex with a lot detail images file sizes are larger then those with little detail.  Noise is like a lot of detail if the images are old and noisey try noise reduction before Save for Web and if that does not work add in some Save for web resize interpolation.

What are the pixel counts (horizontal x vertical), Kevin?

-Noel

It is literally impossible for a 1000 x 1500 pixel image to be saved into a JPEG file that is several hundred megabytes in size.

So either you're confusing megabytes with kilobytes, you're doing something odd like saving in another format that preserves layers and you have bizillions of layers, or you have something terribly wrong with your system.

Please put up some screenshots with your file sizes showing.

-Noel

Interesting concept...  A small JPEG with a truly huge dataset embedded as metadata.  Talk about backwards.  Might cut down on illicit copying though.  

Let's see when the screen grabs are posted. 

-Noel

SFW = Save for Web

I can see how accumulating metadata can result in a big file, though even your example, Chris, is less than 10% of the 450 mb size mentioned.  That would still be hard to achieve.

In any case, it appears Kevin accidentally confused the abbreviations for megabytes and kilobytes, and JJ's advice to try to prep the image for better compression by reducing noise is right on.

But Kevin, keep in mind that if doing so degrades the image's appearance, then it might just be better to post a larger file online in this case, as an exception.  Half a megabyte online isn't as big a deal as it once was...  Internet speeds continue to go up around the globe.

-Noel

Using the default settings, Save for Web will automatically strip the file of its metadata.

Not moot, just tangential.

I would try what JJ said and experiment with some Noise Reduction.

A quick example-  here is an image of your target size (1000 X 1500) made of two passes of the Add Noise Filter in PS (one color one BW) and with a zero quality setting in SFW, it still comes in at 480 KB!

And I run a 10 px Dust and Scratch Filter... produces a JPG of just 20 KB when SFW at zero.

Note, these are extreme examples, but gives you an idea of how a JPG format size can change based on the amount of detail in the image.