[Sholmesy]

That's a hard question, based around the market sentiment of the new coin.

In theory, yes, the value is split. The value is only derived from speculation, and the speculative value of the coin 1ms pre-fork must be the same as the value of the two coins 1ms post-fork, since otherwise people would simply buy immediately before the fork, and then sell immediately after, driving the prices to an equilibrium.

In reality, this is what has happened with this fork hype, people were buying w/ the idea of getting a 'free' coin, like how last time the value of Bitcoin + Bitcoin Cash was far higher than the original pre-fork value of Bitcoin. However, this has driven the price up, causing there to be even MORE hype, which will likely see the price of Bitcoin stay high, since it is now "trending up".