I never send money for an autograph unless 1)they have a signing fee or 2)it's via venue and I offer to make a donation to the school or a charity that the event supports because I'm asking them for a favor that they normally wouldn't do.

In the latter case, I send $20. Or I may send the event fee, particularly if it's a dinner, and ask that what I send pay for the speaker's dinner.

Pretty much just the recommended price if you wish to be generous when sending the autograph. Don't really know how to make it any simpler XD. Like when I send to the spongebob cast they recommend $25 per cast member.

I'm not sure what you're asking - a guide to how much an autograph is worth? What the average price is to get a person's signature? How much a donation to send when asking for a celebrity's autograph?

Is there like a general autograph price guide if you need to send money via mail?