The rewards are being determined by the inquirer. But usually they post the minimum amount needed 0.0001 BTC.
In the F.A.Q I've written
How much should i tip?
As much as you think the tip that you want is worth. The higher the reward though, more members will be interested on answering your question.
Yeah I completely understand that ,its not your fault.Just saying that I don't really put my time finding stuff from low rewards.But happy for the locking threads part.Cheers.