Just a guess here but I'm pretty sure mosts businesses calculate labor costs as the costs they pay their own employees, but looking at labor costs as a means to analyze society means you probably need to include the labor portion of services they receive from other companies (delivery drivers, factory workers who make the business's machines, ag workers who planted and hargested the food, marketing guys who come up with ad campaigns for them, etc) if counting whenever someone is getting a wage or salary somewhere in the supply chain, I could see the number being way higher than what the business owner defines it as.

Material and shipping cost components are each just a sum of labor + surplus. For almost everything, someone somewhere is working to make it happen and receiving a wage for it.

I did a bunch of the math here. I just realized I was calculating based on an average of 20 hours a week at minimum wage jobs, which is probably too low, so I fixed it; the figure would be somewhere between 8% and 12%.

I got the total wage disbursement from either the Fed or the Treasury. Later on, though, I realized that this figure only applied to companies, and I'd neglected to account for proprietorships and partnerships where the owner-operators are not paid a wage. So I looked up the revenues from each, and each is a little over $1 trillion. That still comes out to less than 50% of GDP. And if only $13T-14T of $29T goes to wages, that's still about 53% going to capitalists.

It also does not include the informal economy, and that's a lot harder to quantify, but I make the assumption that there are no key stages of production that fall into the informal economy. Otherwise, there would be substantial traceable tax fraud.