I just added the value of the drops (from drop tables).
Gems from rare taluses are worth about 520 rupees on average
Silver lynel parts are worth 700 rupees. If you cook them in 5 ingredient recipies you can essentially double the value. (Not to mention the arrows bows and shields)
For real. The upgrade costs are honestly massive when you consider how little everything sells for.
I find the economy is fine if you are a completionist who does not use a guide. If I need money I cook and sell the food, or help the monster control crews, or sell rare gems after raiding caves.