The naturally available building blocks are freely available cofactor metabolites from cell organism in metabolic reactions, such as ATP and NADPH, and a list of such molecules curated by Blaβ et al. was used for the naturally available building blocks. The price for these naturally available molecules is zero. In the enzyme-based industrial processes, although the natually occuring molecules are free to acquire, some of these molecules, specifically co-factors, are difficult to recover and recycle, which makes them economically unviable. The common industrial solutions include stoichiometric design that balances each cofactor occurring in the total pathway, or integrating multiple pathways to link the generation/degradation of cofactors. For simplicity, in this work we only consider the acquisition price of the building blocks to demonstrate the overall approach; the cost of separation and other process 'costs' of the syntheses are deliberately left out from the current study.