While $49 isn't something you'd want to spend if you don't have to, it's a one-time expense for the ability to watch online content on a second TV. Yes, you could spend more -- $59. $79, or $99 -- depending on what features you want (1080p instead of 720p, remote for games, etc), but the basic $49 model might suffice.
If you have a Netflix account, you can tie it to a second Roku. They'd share the same user queue, but you can watch separate content on each TV. Same thing with Hulu+. You won't need a second account; you can tie your Hulu+ account to the second Roku. Again, same shared queue, as with Netflix, and you can watch separate content on the second TV.
I have a second Roku on a second TV. I don't use it much, but it's nice to have if I want. If your situation is one of two primary TVs -- for instance, one the parents watch, and another that the kids primarily watch -- then a second Roku may be best way to go.
Roku 3, Roku 2 XS, Roku XD