Offer your thoughts or opinion on the input financial query or topic using your financial background.

Do market shares exhaust?
As @ApplePie pointed out in their answer, at any given time there is a finite amount of stock available in a company. One subtlety you may be missing is that there is always a price associated with an offer to buy shares. That is, you don't put in an order simply to buy 1 share of ABC, you put in an order to buy 1 share of ABC for $10. If no one is willing to sell a share of ABC for $10, then your order will go unfilled. This happens millions of times a day as traders try to figure the cheapest price they can get for a stock. Practically speaking, there is always a price at which people are willing to sell their shares. You can put in a market order for 1 share of ABC, which says essentially "I want one share of ABC, and I will pay whatever the market deems to be the price". Your broker will find you 1 share, but you may be very unhappy about the price you have to pay! While it's very rare for a market to have nobody willing to sell at any price, it occasionally happens that no one is willing to buy at any price. This causes a market crash, as in the 2007-2008 financial crisis, when suddenly everyone became very suspicious of how much debt the major banks actually held, and for a few days, very few traders were willing to buy bank stocks at any price.