Would that happen to be a Marlin Crawler / Experience El Dorado T-Shirt?
I'm not certain. It would require a little research. Autographs that include a certificate of authenticity or verified are worth more. It's a specialized show that would likely require a special fan or collector.
From what I've seen and experienced, memorabilia doesn't seem to do very well, here on OfferUp. Way, way too many lowballers looking to grab these items. The majority of the rest, don't have a true knowledge about the cost and/or value for some items.
Do some searches on eBay, and know sometimes, those prices for memorabilia don't tell the whole story. Way too high on many items.