Stop wasting your time on EBay cheap Nirvana!!!
And our time.
amen and praise the lord
I believe it's safe to bet that there are no "cheap" or "bargain" Nirvana signed items.
If it's on eBay for a low price, 99.999% chance it's a fake.
Unless someone was a total fool, anyone with a real Nirvana would send it to a high profile auction house and/or have credible authentication to maximize return.
Study Nirvana autographs, especially Cobain, and learn how to identify obvious forgeries like these yourself.
Newer collectors and members should show us anything they're considering. But long time members like you are supposed to learn from the vast information here, weed out the obvious fakes, then show autographs for opinions before they buy.