Why are my PSD manually created collages so large?

[alisond24666469]

I have created a set of simple photo collages manually (using shapes, jpgs and clipping masks).  However the resulting .psd files are huge (one is over 2GB).  The collages have 15-16 photos and shapes, (each photo is around 3-5MB jpg) and one simple text layer.  The overall size is A4, with 300 pixels/inch resolution. Can someone explain why the collage files are so large please?  I can't attach a .psd file as an example as they're so big, but here is one saved as a .jpg (size 1.9MB) to show the type of thing.  The .psd I saved it from is 1.92GB.. Many thanks!

[alisond24666469]

Meant to say, created in PSE 2014.  I now have PSE 2024 as well.

[Glenn 8675309]

You have multiple layers, you have multiple images.  You're using 300ppi.-- sometimes it is that simple.  Really no reason to worry about the size of files in todays world- unless you you still have dial up speeds.