unpayable
/(ˌ)ʌnˈpeɪəbl/adjective
1Of a debt, charge, obligation, etc.
2Originally and chiefly Australian Mining. Incapable of yielding an adequate return; unremunerative, unprofitable.
Origin
Early 16th century; earliest use found in George Ashby (d. 1475), administrator and poet. From un- + payable.