It's not relevant to compare to Firefox or Chrome memory usage.
They are both programs that are constantly used. Tabs and windows are opened and closed. Memory is reserved and released.
The Endpoint SQL process eats 300MB at idle. Doing nothing. It's not waiting for a request that cannot be foreseen, like instant messangers or Skype would do.
If you want to compare Firefox to Endpoint, my Firefox uses 200MB (private) while doing nothing. No open tabs, freshly opened.
Attaching my sqlservr.exe process info. It is at idle, consuming 300MB memory (private).
It's a Windows 7 laptop with 16GB memory and a 120GB solid state disk.
I'd be very happy if it would run with the numbers you are posting, 22, 55 or even 90MB.