You just summarized Marx's labor theory of value. I'll explain why it was refuted 130 years ago, without any hard feelings.
The idea that value comes from labor has a fundamental problem. If I spend 400 hours building an ugly chair that no one wants to buy, it isn't worth more than a chair built in 2 hours that everyone snaps up. Value doesn't come from the time spent.
It comes from what someone is willing to pay. That's the marginalist revolution of 1871 (Menger, Jevons, Walras), confirmed by BΓΆhm-Bawerk in 1896, which formally demolished the labor theory of value.
This isn't an open debate. It's been settled for over a century in the economic literature.
Now, "the owner extorts the surplus value." Extortion implies coercion. But an employment contract is voluntary. No one forces you to sign. You can leave tomorrow. You can start your own business. You can go freelance.
And above all, the owner doesn't "take" anything. He takes a risk. He advances the capital. He pays salaries BEFORE the product is sold. If the business goes bankrupt, the employee gets unemployment benefits. The owner loses everything.
His savings, his time, sometimes his house.
The "surplus value" you describe is the compensation for that risk. Without someone to advance the capital and organize production, the worker produces nothing at all. Ask any freelancer: the hardest part isn't doing the work, it's finding the client and structuring the offer.
Last point. If labor alone produced wealth, the countries with the most workers would be the richest.
India and Bangladesh would have a higher GDP per capita than Switzerland. That's obviously not the case. What makes the difference is capital, innovation, organization, and institutions.
I'm telling you this without any animosity. The labor theory of value is appealing because it's simple and it has a hero (the worker) and a villain (the boss). But economic reality is more nuanced than that.