I'm not an expert on this but I think the point was market cap is the value of all outstanding shares. Tesla raised money through venture capital while GM raised money by going to the bank and getting a loan.

Think about buying a $1M rental property. One guy gets 9 friends together and they each put up $100k for 10% of the house. The house/business is worth $1m. The market cap is $1m.

Another guy wants to buy a $1m rental property but he goes to the bank and gets a $900k mortgage. The house is worth $1m but the market cap is only $100k.

Since tesla and GM raised money very differently their market caps are not comparable.

The house's market value is the same as its market cap. It would still be $1m in both cases. How it was raised is irrelevant; you won't find a buyer for less or more than $1m if that is its market price.

GM and Tesla are both public market stocks. Regardless of how they raised previous capital, the market is valuing Tesla higher.

"The house's market value is the same as its market cap."

That's because houses are quoted in total, not just the equity piece. Stocks are only the equity. (They could quote just the equity piece of houses. In that case it would be unhelpful to compare prices without checking the debt.)