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I got 4.54 EPA

<img src="/w/index.php?title=Special:MathShowImage&hash=a9464febc314c32d725fa0eda9d845f7&mode=mathml" class="mwe-math-fallback-image-inline" aria-hidden="true" style="vertical-align: -2.005ex; height: 5.843ex; width: 82.59ex;" alt="{\displaystyle {(4*85/100+62.5*15/100)*1/2+(6*0.15+25/2*0.05)*19*5+312.5-0.3} \over {2+20*5}}"/>

I assumed Eyeless Skull chance of 5%, Rare Success on sale 15% as you suggested, and subtracted the <a href="/wiki/Piece_of_Rostygold" title="Piece of Rostygold"><img alt="" src="/w/images/thumb/5/50/Red_gold.png/20px-Red_gold.png" decoding="async" width="20" height="26" srcset="/w/images/thumb/5/50/Red_gold.png/30px-Red_gold.png 1.5x, /w/images/thumb/5/50/Red_gold.png/40px-Red_gold.png 2x" /></a> 10 x <a href="/wiki/Piece_of_Rostygold" title="Piece of Rostygold">Piece of Rostygold</a> from the total (Bazaar priced)