I've played ESO tonight (germany, 8PM) and get a loss of around 3 Gigabytes RAM. That's since a couple of weeks, but never had it so hard.
Hardware :
Sony Vaio E-Series
Core I7
AMD Radeon 7650M
6GB RAM
250GB SSD
1TB HDD
Windows 7
Screenshots attached
first shows usage of ESO Client 1.8 GB RAM, but total loss of around 3GB
second shows with closed ESO Client and Launcher