> First off, the 86T figure is the yearly GDP of the world whereas the 2T figure for Apple is the value they are worth to shareholders in perpetuity. Not directly comparable.
This is a good point, the market price for the shares corresponds to cumulative flows of expected net profits accrued over many future years. To add more detail, when I do a crude discounted cash flow valuation of AAPL assuming very optimistic revenue growth (+15%) in the short term that decays to 2% growth after 5 years or so, & using a discount rate of 6%, that backs out a value per share estimate of around $134 , with the majority of that valuation -- $76 out of $134 -- being contributed from net profits that occur after a 15 year time horizon. The current market price for each share incorporates the assumption that AAPL will continue to be a profitable business for decades, maintaining comparable profit margins, with at least some degree of revenue growth that outperforms economic growth in the short run.
If we assume AAPL is afflicted by some weird calamity that causes it to have exactly 0 net profit over the next 12 months but then otherwise bounce back to its usual profitability, that should only reduce the valuation of each share by about $4 -- a 3% drop in share price .
Similar kinds of reasoning can be used to estimate how much the valuation of shares should drop due to COVID-induced short term loss in revenue & profitability -- e.g. it might roughly be something like a single-digit percentage drop in value -- say 6% ish -- (industry and company specific, some sectors such as hospitality and travel suffer more impact, and companies with heavy financial or operational leverage may have much higher short term losses in response to the same drop in revenue, perhaps going bankrupt). Compare to the 33% drop in market prices in march earlier this year.
My discounted cash flow valuation for AAPL assuming a pessimistic revenue growth scenario is around $70 / share -- so I value each AAPL share somewhere in the range of $70 -- $134 & won't be buying any while the market price sits at the high end of that range.