^
because it costs to setup plus own server costs
lowered to 0.02 BTC for a weekly plan or 0.08 BTC for a monthly plan
like follow plus retweet will be 0,0005 BTC after a few more orders
But anyone could just send you wording and ask you to tweet it 14 times at 2/day (I don't expect you would reject such request). The total costs at current rates would be
BTC0.0056, so
BTC0.0144 cheaper than weekly plan with exact same result.
In other words, for 0.02 I could get 50 tweets rather than 14 (weekly plan).
By definition, fixed plans should be significantly cheaper than one-time service, not the other way around.