Promotion of sites and blog in twitter is a good idea and also good for seo factors. But your rates are too high.
You are charging 0.05btc per week. I think you should think twice about your rates. Now a days too much advertisements are coming on twitter that's why people won't click any blog link on twitter. So most of tweets and retweets give nothing.
i don't think the price is high.i am not giving fake re-tweet or likes so when someone buy the special package will get some real bitcoin users.Actually i think its a cheap way to get in touch with bitcoin users.
Regards