The expansion Xia: Embers of a Forsaken Star is available for $50 (the price I paid for it when I originally posted this 5 months ago) from the Far Off Games Amazon storefront > https://www.amazon.com/Far-Off-Games-Xia-Forsaken/dp/B06XPMM874?source=ps-sl-shoppingads-lpcontext&ref_=fplfs&psc=1&smid=A246OZDOV2A00D

At the moment, neither the base game nor the 2 other expacs are showing in stock, but when I originally posted this they were getting restocks fairly regularly.

I don't know if that still is the case as I have not been tracking them lately, but I would advise you to keep checking their storefront on Amazon.