What are the tangible benefits of using a professional wheel building and truing service, particularly when it comes to high-performance, fixed-gear applications where every gram of weight and every increment of aerodynamic efficiency counts? Is it solely a matter of achieving a perfectly true wheel, or are there more nuanced advantages to be had from a custom-built wheelset, such as optimized spoke tension and lacing patterns, or the ability to select specific components and materials tailored to the riders specific needs and preferences? How do the benefits of professional wheel building and truing compare to the costs, and at what point does the law of diminishing returns come into play? Are there any specific scenarios or riding styles where a professionally built wheelset is an absolute necessity, and if so, what are the key factors that distinguish these situations from those where a mass-produced wheelset would be sufficient? Can anyone speak to the differences in performance, durability, and overall riding experience between a high-end, professionally built wheelset and a comparable, mass-produced alternative, and if so, what were the key takeaways from their experience?