In general
Let me spam you another answer: Svg file size more than a png image
Here is a graph where the x-axis is the pixel size and the y-axis is the file size.

A vector file is mostly independent of the dimensions and a raster image is proportional to it.
But that is not the full story.
Now let us think in an uncompressed raster image vs a vector file both with fixed dimensions. But now let's change the x-axis, now it is "information".

You can have one tiny or several circles defined in the image. On a bitmap the diference will be the color of the pixels but the pixel count is the same. The size of the file will not change.
But now put two circles on a vector file vs one. You have doubled your information. Let us think something like:
<circle cx="50" cy="50" r="50" stroke="black" stroke-width="5" fill="black" />
Now put 3, 4, N circles.
<circle cx="50" cy="50" r="50" stroke="black" stroke-width="5" fill="black" />
<circle cx="50" cy="50" r="50" stroke="black" stroke-width="5" fill="black" />
<circle cx="50" cy="50" r="50" stroke="black" stroke-width="5" fill="black" />
<circle cx="50" cy="50" r="50" stroke="black" stroke-width="5" fill="black" />
The increase in the information is linear. The information will increase for any new feature added to your file.
On your specific image
You have a shadow. This can be an actual bitmap for faster processing or could be the instructions on how to re-render it each time. This can make a difference in file size, but also in processing time. Imagine you need to repeat the instructions each time.
On your update, you mention linking an external photo to a file. On a PDF file, there are not linked files. They are inside the file. The file inside could be resampled, and compressed, or not depending on the settings. It can also have fonts converted as curves or the font file embedded or not.
On a native file you have the file actually linked, but with a preview embedded.
Conclusion
There are a lot of factors to consider thinking about a file "weight". Vector information, instructions, raster effects, raster images, preview, scripts, layers, embedded information, objects not displayed, etc. You can not think about file size just in terms of vector vs raster.