For me I can only accept autographs I've gotten personally. So it doesn't matter if I get an offer for 5, 50 or 500 Dollars, they could all being fakes.
you have to remember ebay is full of crooks..i saw an autograph of brian for sell on ebay said it was signed by him in 1971..lol...he died in 69...ebay the crooks paradise
i always wonder why people want autographs they didn't get directly from the person - i mean, the experience of getting it is the cool part, isn't it? the ink is just a memento of the occasion, at least for me.