Hmmm, this really is an opportunity to get a little nasty… It depends what you have access to. If you have a well stocked witch cupboard, I’d wrap the notes (absolutely give the extorter the money in cash) in something nice and baneful while visualizing wrapping the person in misery and bad luck (A few datura leaves will have a good impact.) You could try sticking some rue in there as well, nice and itchy! Mistletoe oil has a powerful baneful kick, so in addition, try saturating one of the notes in that.
If you haven’t got access to this kind of stuff, I see no reason why things from your kitchen cupboard won’t work just as well. Basil is associated with monetary wealth, so try doing a wealth reversal spell. Take the money and place in a bowl with a few heaped tea spoons of either fresh or dried basil. Stir the money round the bowl anti clockwise and use a simply worded spell, something like:
“Fortune change, fortunes reverse
Your wealth to take a change for the worse”
Take the notes out slowly one by one and visualize the personal finances of the person slowly ebbing away as the funds are removed. Hand the funds over personally in cash.
You worry about the curse coming back to you – that’s quite a new age/Wiccan concept. Its not an idea I subscribe to, I curse away quite happily and nothing has ever pinged back at me. If it makes you feel better, think of it as justifiable defensive magic, you are not doing the spell out of malice – the other person started it. Really, you’re just balancing the universe!
Incidentally, why are you letting this person extort cash from you? Are you being blackmailed? Are you sure paying them is the best idea? Normally blackmailers keep on wanting more and more and are rarely satisfied with a one off payment… Are there no other alternatives?
Image http://www.sxc.hu/photo/1185031 (foxumon)