The price? I am guessing you are not in the UK strider?
But actually price isn't really relevant. This would just be a form of Lithium and I imagine there are a considerable number of people here who have been on Lithium either in the past or still are; I was on it for some years. I must admit I am a little surprised about its being prescribed as a main treatment for depression initially rather than a back-up or addition to some other anti-depressant which it always was in my case. In general (and I emphasise in general - you should ask a professional for specific advice) Lithium is used firstly as a so-called 'mood stabiliser' in treatment of BPD (Bi-Polar disorder) and secondly in cases of recurrent depression where other anti-depressants have not worked.
In practice (in the UK anyway) I think it is usually used where depression is concerned - as in my case - in conjunction with an anti-depressant.
The warning about Lithium is that the way in which it works is by having a certain level in the blood - if that level rises too high then there is a danger of lithium toxicity (symptoms include loss of appetite, diarrhoea, vomiting, blurred vision etc.) so you should see your doctor immediately if you do experience side-effects. Lithium can also potentially affect kidney function. Anyone on Lithium should be having their blood tested periodically but I am sure you have been told this.
As to the $100 question

- well whether any drug works or not is entirely individual. If it is working for you great. I am sure that there will be people who could supply both positive and negative responses.
Nick.