heavy metal machine cassette: almost worthless. $5 maybe? maybe a bit more because it’s sealed. but i doubt there will be much interest for this.
signed lithograph: the lion lithograph seems to be the most common one. i think it is worth about $15-25. not sure how much extra the autographs will add. it’s always hard to put a price on that.
if you sell them on ebay, and more people are interested, you might get a better price for the cassette.
i don’t know for how much you want to sell the lithograph, and for what price you’d rather keep it, but maybe you can put a reserve on it, or start the bidding at your minimum price.
or maybe someone on here is interested in buying it directly from you?