I haven’t done the same thing yet for memory utilization vs repo size (at least, not yet), but I collected some memory utilization data vs peer count using a simple bash script I wrote for logging ipfs daemon memory usage, repo size, and peer count over time.
At least for an idle daemon on v0.4.10, each additional peer on my idle laptop consumes on average a bit less than 0.5 MB. I suspect this graph would look very different for an actively used daemon, but it should be straightforward to reproduce different test scenarios (e.g., offline daemon while adding content to repo, online daemon while adding content, online daemon pinning content, etc) as desired while capturing the relevant metrics with the script and then analyzing them afterwards to look for trends. In case it matters, the repo size is pretty much right around 8.9 GB for all of these data points.
The connections alone don’t seem like they could account for 2 GB (or 4 GB) of memory usage since I’ve never been connected to more than about 700 peers, so I’m guessing there are some other significant factors.