Some people literally take 5 seconds to make one and yes, will charge 2 million for them...
Just google free sig generator or free sig creator....
However, if you want a good signature, something that actually took time, check out the graphics forum, tho you'll most likely pay anywhere from 10mil to 50mil depending on what the "artist" wants for it.
Depends, these ones took me ages, I charged Krak about $50m, Evil-Duck's was free as his money was tied up in DB's. So if you want quality like the ones below I think you get what you pay for.
If you fancied trying yourself, you could download gimp or if you have ps then just google search "gimp sig tutorials" (obviously substitute gimp with ps if your using photoshop) and have fun