I thought share valuations were based on a company's net asset value.
That is only a tiny fraction of the valuation.
For example, a a MASSIVE and hugely profitable consulting firm, might have assets that consist of a few thousand laptops and the desks and chairs. Maybe $10 million in assets? They might have $50 billion in revenues and $2 billion in profit and be worth many billions of dollars as a company.
On the other hand, a company that smelts steel at a loss might have $100 million in assets but only $10 million in revenues and suffers a $3 million per year loss. This company may actually be worth LESS than their net assets, depending on how bad their debt situation is, and what kind of outstanding obligations they have.
Realistically, I think the share price of a company is simply set by people's estimate of the value of the company, divided by the number of shares a company tries to sell.
Say the company decides to sell 1 million shares (this is an arbitrary number) that represent a 40% stake in the company. If the investors believe the offering is worth $10 million, they will pay $10 per share for them (since there are 1 million). If they, instead, only offer 100,000 shares, the same investors will pay $100 each for them (since there are 100k of them). Both are essentially the same thing, although one is harder to divide into smaller chunks.
In practice, for psychology reasons, businesses seem to like to keep their share price around the "every day" that people are used to. This means they release a number of shares that will make each one worth between $5 and $100.
When the value per share gets very high, often they "split" the shares, making each one half the price (but you get double the number). Someone who paid $100 for a share suddenly has two shares worth about $50. Nothing changed except the psychology of it. People hesitate to shell out for shares that are $800 each, and also hesitate to buy "junk" that is worth less than $5. Just psychology, though, because those numbers mean little without accounting for the actual market capitalization (total shares times share price).