I don't think I'm knowledgeable enough about this subject to give you a complete answer. At some point I tried to have a better understanding of the US healthcare system due to its unique features but unfortunately it still eludes me somewhat.
In any case for your question "How can something that costs $3000 have a reduced cost to $450 just because I have insurance?" the important concept to understand is Chargemaster:
In the United States, the chargemaster, also known as charge master,
or charge description master (CDM), is a comprehensive listing of
items billable to a hospital patient or a patient's health insurance
provider. In practice, it usually contains highly inflated prices at
several times that of actual costs to the hospital. The
chargemaster typically serves as the starting point for negotiations
with patients and health insurance providers of what amount of money
will actually be paid to the hospital. It is described as "the central
mechanism of the revenue cycle" of a hospital.
So the real cost (assuming the hospital is not operating under profit) for the $3000 service is actually somewhere below the $450. The $3000 value is a starting point for negotiation. As for your second question "To me, a basic public "price list" seems like a foundation to a business. Why isn't that so?" there are some efforts to bring transparency to this sector:
Updated March 2017: In the past decade, health care price transparency
or disclosure has emerged as a hot topic in state legislatures, as a
strategy for containing health costs. States, the federal government
and the private sector have enacted legal requirements and initiated
programs that aim to shed light on the costs of health care services.
According to wikipedia some states (California) have legislation for this:
In California, a regulation known as the "Payers' Bill of Rights"
(which is unique to the state) requires all hospitals to provide their
chargemaster to the state, which then posts them online for the
public.
You should also be aware that this (as in the actual healthcare system) is a contentious issue (often even outside the US). A possible analysis for the cost of the US healthcare system is:
Unlike most markets for consumer services in the United States, the
health care market generally lacks transparent market-based
pricing. Patients are typically not able to comparison shop for
medical services based on price, as medical service providers do not
typically disclose prices prior to service. Government
mandated critical care and government insurance programs like Medicare
also impact market pricing of U.S. health care. According to the New
York Times in 2011, "the United States is far and away the world
leader in medical spending, even though numerous studies have
concluded that Americans do not get better care" and prices are the
highest in the world.
You'll find plenty of other resources on the subject both from media,
independent organizations, or academia (see also: resource1, resource2).