Tesla's electric semi is moving toward real production, and that pushes the long-term case for the stock higher — good for patient shareholders, but only if the math works out.

• Tesla shares rose 4% on news that the semi truck is nearing volume production, with test trucks now carrying self-driving sensor gear.
• California is the key: state green-truck subsidies can cover roughly half the truck's price, and rules force fleets to go electric over the next several years.
• The pitch to buyers is running cost — an electric semi costs about half as much per mile as diesel, paying for itself in about five years.
• Adding stronger semi profits lifts a 2030 price target from the mid-500s toward roughly $590, and a big Optimus robot business could push it near $670.
• The catch: on this year's earnings, Tesla still looks expensive, and profit margins are thin at around 5%.

Outlook: The stock looks like it may be putting in a bottom, but the real test is whether margins recover — and 2030 hopes have a habit of arriving late.