We know that The Elder Scrolls Online is one hell of an undertaking for Bethesda. ZeniMax Online Studios have been working on the title for quite some time, and apparently the development cost is in the multiple hundred million dollar neighborhood. Reports from a reliable industry source cite a $200M price tag for development thus far.
Many have questioned the monthly subscription model that The Elder Scrolls Online will employ, but when you consider that enormous development budget, things become a bit more clear. Hopefully the studio has planned ahead with tons of end game content to keep players coming back for years to come, or The Elder Scrolls Online may be headed for disaster.