TDG transdigm: what am I missing here?

TDG has one of the widest economic moats in the industrial world. * **Regulatory Barriers (The FAA):** In aviation, you cannot simply swap a part for a cheaper generic version. Every part must be FAA-certified. For a competitor to copy a TDG valve, they would have to engineer it, undergo years of testing, and spend millions for certification. * **Switching Costs:** Since TDG parts are often small and cheap relative to the plane (e.g., a $5,000 valve on a $100M plane), airlines have zero incentive to risk safety or undergo recertification just to save a few dollars. * **Installed Base:** TDG parts are on almost every commercial and military aircraft in service today. This guarantees a stream of high-margin replacement revenue for decades. Solid growth of 10-20% annually. Operating margin around 50% (this is operating margin, not gross margin). 6.39% dividend and they annually do special dividends on top. PE around 40 which is not terrible for the growth and the margins. I won't go over the bullcase which is obvious for this monopolistic business: inflation, rising geopolitical tensions and defense spending leading to airplane service booms (I hear every plane both military or commercial uses their parts), return to normal airplane travel in the post-covid era needing more plane construction and servicing. Only main downsides I see are 1) high debt: total debt is 5x annual earnings (something I don't fully understand) 2) the business model is slightly unethical. They have a monopology on many parts, sell them for cheap to get them incorporated into airplain designs and then jack up the price for replacements in the future. They also buy out small competitors to eliminate them regularly. There have been accusations of price gouging (which as a capitalist I'm not sure is a bad thing) Still they beat the market over the last 5 years and would have beat last year but had a poor q3 report which led to a selloff. Stock price is rising again. What am I missing?