I don't actually understand how Ooma can work at the their current rates, and $200 is really expensive for a device like that.
Here in the US, Cellphones are free since they come with your plan, I hear in Europe the phones cost a mint, but the monthly fees are lower. I have no idea what the device ought to cost ( prolly cost them $1.95 in parts ).
If you have a contract, at least in the UK most phones are free, top of the line smartphones are not but only require a nomial fee. If you are on pay'as'you'go though then its a different matter.
The biggest mistake you can make is to believe that you are working for someone else.