Doctors must remember that the way we determine what "normal" values are is by fitting large samples to a bell curve, chopping off the ends at 1 or 2 standard deviations, and calling the middle "normal".
Well, it all depends on the disease/condition. Gout is a disease diagnosed by certain symptoms. Having those symptoms w/o high uric acid is still regarded as gout, while high UA w/o those symptoms does not merit treatment. However, there are diseases that are defined by lab results, and not because we are looking for extra patients but because early recognition and treatment can prevent morbidity and mortality. For example, Diabetes is defined as fasting glucose above 126. The reason is that people who have a higher fasting glucose level have a greater chance of complications (heart attack, stroke, kidney trouble, vision loss, etc.). Early treatment may prevent these complications. The same is true for hypertension and other diseases.
Another issue, is screening for diseases before they erupt, for example, mammography for breast cancer. Yes, breast cancer screening may save only 1 life in 1000 over 10 years. However, many other women will be diagnosed earlier and thus may need smaller surgery (for example Lumpectomy. which preserves the breast vs. Mastectomy, which removes the entire breast) and less systemic treatment (i.e. chemotherapy and radiotherapy). On the other hand, some women will have false positive results and the cost and suffering of doing a work up for a benign breast mass should be taken into account when suggesting a screening procedure. This is part of the reason why there is an argument about the age above which to recommend mammography for women (40 vs. 50 years old).
Regarding the cost-benefit ratio, saying that a drug saves only 1 life in 100 is misleading. What is the cost of giving 100 people cholesterol-lowering drugs? Most of these drugs cost pennies and their side-effects are, usually, negligible.
Yes, thresholds for treatment are being lowered. Sometimes because of bad reasons, such as covering your ass from malpractice suits and industry lobbying, but most of the time it is due to greater understanding of disease (esp. the early stages of diseases) and better and safer medications.