Hardware startups universally face 3 major problems
GETTING TO MARKET
Hardware companies spend inordinate amounts of time and money just to launch a product. Burn is not driven by prototyping or manufacturing, but the increased team size necessary to ship a hardware product.
RAISING SMART CAPITAL
Many investors aren't comfortable investing in hardware companies. Discomfort is driven by fear of the unknown. Most VCs are far more comfortable if domain-experts are already on the cap table.
Manufacturing is the leading cause of hardware startup death. But this isn't due to manufacturing itself, rather a poor understanding of product design and common timelines. If you've done it before, scaling isn't hard.