jonathan hit it on the head, it's a numbers game.
If it's a group health plan, the docs and the insurers in the group somewhat decide on the pricing for that group and for a particular area or zip code. Health care/benefits administration is a very tricky business in the US and the insurance companies are taking on a liability but we all know that they profit.
Think about all the money residing in a coffer so-to-speak and then being invested by pro's and being used to pay actual claims. The insurance companies wouldn't make any money if they couldn't cover the claims and they work hard to ensure they don't lose money.
Some companies fund their own plans as well and take that liability on themselves, but decisions like that are typically based on the company's claim "experience" and the company's demographics as there are various liabilities associated with different demographic groups. That "experience" also drives the price of insurance for a company.
I personally like the concept of an individual participating in a Health Savings type of plan from an individual's first day of employment and letting that balance add up over the years, as you switch jobs or whatever. Hopefully, taking the liability away from the insurance company and driving down some of the cost. There will always be instances where you can't afford the claim, but similarly instances where you haven't personally made a claim for an entire plan year.
The story of employee benefits is that the company sponsoring a plan/program receives wonderful tax breaks for offering and maintaining that plan. The employee receives a tax break for the monies they put towards it (IRC, section 125c). Typical employer and employee splits on the premium cost from the health insurance company are around 80/20. However, the folks that do the design and valuations and such on the plans are highly intelligent and very well compensated (actuaries) and the administration of the plan is very low profit (plan administration). Which if you work for a big organization in the US is most likely being done halfway here and halfway over seas with the aid of some customized software with one of the large HR outsourcing firms. These types also have huge budgets for errors and omissions (read administration mistakes).
It get's even more shocking when you see how this works for retirement plans (401k's and traditional pension plans). The basic premise for pensions initially was tax deferment for owners as they would save more by spending money to provide an annuity to what they refer to as the "rank and file" workers than they would paying the taxes on high compensation year after year. Companies collectively began offering various plans (health and retirement) to employees to stay competitive for talent back when people used to work for companies from high school through retirement. Things have changed dramatically amongst the work force (job hopping, etc) since then and benefits design tries to keep up with that by offering immediate vesting in contributory plans (401k, 403b) and cash balance designed defined benefit pension plans.
None of this discounts that an MRI is an expensive procedure on account of the equipment, etc. Just trying to shed some light on the back workings of employee benefits plans and how that plays into what an individual pays for care.
