Gary Black, managing director of The Future Fund LLC, has a message for Tesla Inc. (TSLA) shareholders: don't believe the hype. On Friday, he issued a pointed warning to remain skeptical of the glowing analyst commentary swirling around Elon Musk's other giant venture, SpaceX.

"Be wary of sell-side analysts' overly positive opinions about SpaceX, a TSLA/SpaceX merger, or the merits of any specific IPO," Black wrote on X. His core argument cuts to a fundamental tension on Wall Street. He notes that sell-side analysts—the ones at big investment banks who publish research and price targets—are paid based on commissions. Their paycheck is tied to generating trading activity and banking deals, not necessarily to being right.

The $75 Billion Incentive

This warning isn't happening in a vacuum. It comes as reports suggest SpaceX could file for its initial public offering as early as this week. The space giant is reportedly targeting a staggering $1.75 trillion valuation and aims to raise up to $75 billion.

Black frames this as the ultimate motivator. At an expected $50 billion to $75 billion IPO size, SpaceX represents the "biggest payday for TSLA analysts in years." The implication is clear: analysts, eager for a piece of the lucrative underwriting fees and allocations, might feel pressured to cheerlead for the deal or a merger that aligns with management's desires, rather than offering clear-eyed advice to investors.

The Insurance Salesman Test

To drive the point home, Black used a sharp analogy. "Quoting a TSLA sell-side analyst on the merits of SpaceX or a SpaceX/TSLA merger would be like quoting your insurance salesman on whether you need more insurance," he stated.

This skepticism stands in contrast to other voices on the Street. Analysts like Dan Ives of Wedbush Securities have suggested a merger is "likely in 2027" and could offer a 55% upside to a $600 price forecast for Tesla.

Why a Merger Could Be a Bad Deal

Black isn't just worried about bias; he thinks the merger idea itself is flawed. He has previously warned that combining Tesla and SpaceX could trigger a "20-25% reduction" in Tesla's stock value. His reasoning? It would create a "conglomerate discount."

In finance, a conglomerate discount is the idea that a company with diverse, unrelated businesses often trades at a lower valuation than the sum of its parts. The market applies the valuation multiple of the lower-performing or less-understood segment to the whole entity. In this case, Black argues the combined company would trade at the "lowest common multiple" of the two very different businesses—electric cars and rockets.

"A TSLA/SpaceX merger is a solution looking for a problem," Black concluded bluntly on Sunday.

While analysts debate the future, Tesla shares were down 1.80% at $365.42 at the time of publication on Friday, according to market data.