First, Ctrl+y - or view as outlines to make sure there are no "lost" objects or stray points on yout artboard that may be increasing the actual size of your export.
Than try, File/Save As (a new file). This will often give a slight reduction in file size.
It's possible that you Pasted the rasters into the AI file instead of File/Place - This will make your file size larger. However, Placing the files probably won't make a difference regarding exporting. Check Window/Links to see if the files are linked.
You could try lowering Effect/Document Raster Effect Settings, ,reducing your output resolution, or deselecting Anti-Aliasing or compression.
Can you try opening the AI with Photoshop, to rasterize. Or, File/Save As: Adobe PDF than rasterize with photoshop.
On your second image which is 25 mb, I did a save as and unchecked the "PDF comaptible" and it went down to 10.4mb.
Now I was able to do a save for web, on a Mac withg 5gb of ram.
Your images are embedded which makes your AI file size larger, so you select an image, choose file >> place (and check the link and replace option). Your images will now be linked rather than embedded freeing up disk space and making your saves faster (but do not delete or move the original images or the links will be lost forever or broken until relinked.
To solve your problem I recomend trying an export to tiff(72 dpi), than opening the tiff in photoshop and doing a save for web.
Since your images are embedded, we do not know their resolution, and save for web needs more ram/graphics card power to work than export.
Let us know how things turn out or if you need more help.