All eyes have been on SpaceX (NASDAQ:SPCX) stock this summer, leaving Tesla (NASDAQ:TSLA) to take a back seat. And with SpaceX and Tesla down 52% and 37% respectively from their 52-week highs, now could be a great chance for me to buy these stocks. Specifically, for fully autonomous robotaxis and general-purpose humanoid robots (called Optimus), which Tesla aims to sell to factories, warehouses, and eventually households. This is the profitable engine of SpaceX today, with subscribers now totalling around 13.6m. Unlike Tesla, SpaceX doesn't have any meaningful competition today.