Private aviation suffers under very stringent
regulations that are not always fairly or practically conceived and enforced.
I get very cheap labor, because I do what I must do to keep my planes flying with my own two hands. Sometimes I pay myself with a cigarette, or more extravagently, with a flight just for fun. Small airplanes are far simpler than cars mechanically, and their proper maintenance mostly involves (as its most precious commodity) a generous amount of common sense. Parts are relatively expensive, either directly in purchasing them, or indirectly when it is necessary to fabricate them. In all cases the effort is well rewarded, but not always financially. Most aircraft owners who do not have the opportunity or desire to learn how to maintain their machines typically pay $30-80 hourly hiring someone.
Preventative maintenance is always cheaper than maintenance out of immediate necessity. In other words, aircraft are properly and most commonly maintained with the philosophy of monitoring the entropy of every component, and replacing that component before reliability is in doubt. Some components, like the primary structure, require very little maintenance other than respectful usage and corrosion protection, and can easily serve reliably for a century or more.
On one of my planes, I recently repaired the primary fuselage structure in 2 places due to rust, in the course of an overhaul. I basicly took a hacksaw, cut out the rusted areas of tubing, and welded in new replacement sections of tubing that I made and installed for about $20.
Sometimes due to a deteriorating valve, I will remove an engine cylinder, have it reconditioned by an engine shop with new valve parts, and I'll reinstall it for a total cost around $500. I overhaul engines when they are "ready". This is a decision based not only on hours already in service, but also on oil analysis, engine performance, and sometimes economics- If an engine is requiring any exhorbitantly expensive single component repair, it is exchanged for an overhauled one. Recommended overhaul periods are a vague comparative statistic, but have no useful predictive value regarding one particular engine. Some give good service through 25% of their recommended overhaul period, and some through 150%. Most get overhauled near the recommended TBO(Time B4 Overhaul). Major engine overhauls for a simple single-engine airplane range from $12,000 to $25,000 depending mostly on engine power rating. Most engines like this get overhauled once every 2,000 hours on average, which for individual occasional flyers can be literally a lifetime. So far, I've personally flown about 6,000 hours, which is more than typical.
Generally speaking, there is no evidence of any problem with the standards and practices of aircraft maintenance anywhere I have been. Very, very rarely are mechanical problems the cause of any injuries. In the case of private aviation, government involvement has reached the level that any greater regulation destroys the market. In other words, the only way that private flying can be made significantly safer is for the very activity to be economically curtailed. Of course it is likely that somewhere, someone is doing something stupid from a mechanical standpoint, to an airplane- but for the vast majority of people involved, very conservative and sober thinking goes into aircraft maintenance.
About 350 Americans are killed annually in connection with the operation of small airplanes (about 40,000 per year die accidentally in their cars, 30,000 intentionally end their own lives, and 20,000 are killed by violence within the USA). Most general aviation accidents have a chain of factors, rather than one single cause. Most often, as in over 95% of accident cases, the most offending component is the pilot. It would be difficult to find evidence to support a contention that more than a dozen Americans die annually as a direct result of bad aviation maintenance in the private aviation sector. It would be even more difficult to find a regulatory way to eliminate this specific manifestation of human error or negligence.
It is absolutely clear that aviation maintenance is a very rare primary cause of aviation accidents. In most cases bad decision-making precipitates tragedy. Reducing the likelihood of bad pilot decisions is a predominating focus of my work as a flight instructor. As I do routine maintenance on my airplanes, there is little or no uncertainty as to when a job is finished, or done right, and when it is not. Simple machines are simple to keep in good working order.
Some reference links:
General Aviation Accident Statistics (a .pdf file)
Airline Accident Statistics