No, it's not perfectly neutral; both of us could easily find particular people who are more or less screwed over on either side. That's not really the point. The health care deduction rule is specifically designed to approximate the deduction advantages of employer sponsored care, without making it just as easy to quit working.
Challenge accepted. Lay out one scenario where someone would be better off getting paid $x and paying $y for their own health insurance policy than they would be if they got paid $(x-y) and had their employer pay $y for the same health insurance policy. I dare you.
Set up within your constraints, that looks impossible. In part, because you require that my out of pocket costs and my employer's costs be fixed to the same number ($y) which is not how the real world works. But also because, as I already noted, the system is geared to favor
employees in this context. I.E., the working class.
That said, let's see how close I can come. I'm using the 7% AGI rule, btw.
I found out immediately that actual un-subsidized premium costs are not available to myself in my home state of Ky. So I will use the average costs of a bronze plan according to
https://www.healthpocket.com/individual-health-insurance/bronze-health-plans#.Vh3HZlJkZwI as a proxy for a low end, employer provided plan.
Rule #1, only out of pocket expenses above 7% are deductible, because premiums (paid either by employee or employer) are already deductible for someone.
Rule #2, premiums avoid FICA, but out of pocket expenses do not.
Rule #3, co-pay is 40%, deductible is $10,545 (family plan) & max-out-of-pocket is $12,749
Rule #4, our couple is 60 years old, with average monthly premiums of $627
each. Costs of plan to be shared by employer 50/50.
Rule #5, our couple earns the national median household (2012) income of $50,500, so their 7% mark is $3,535.
Rule #6, ignore the standard deduction for simplicity.
Annual premium = $7524 for both the insured couple and the employer, $15,048 total.
Couple has an epicly bad year. Say cancer treatments. Racks up bills right at $31872.50
(40% of $31872.50 is $12,749, is the deductible included in this? I will assume yes)
As employees, this couple still paid $956.18 in FICA taxes on the out of pocket portion of these costs, as did the employer. But managed to deduct $9,214 ($12,749 - $3,535) with a net deduction of $1382.10 (15% tax bracket). This results in an overall reduction in taxes of $425.92 ($1382.10 income tax refund - $956.18 in FICA taxes paid in)
But what if our couple is FIREd, pre-Medicare? In this case, $24,262 is deductible ($12,749 total out-of-pocket expenses + $15,048 total annual premium - $3,535). At the 15% bracket, this is a net income tax savings of $3639.30. FIREd don't pay FICA anyway. So from a tax perspective alone, the 7% of AGI threshold wins. From the perspective that an employer (or taxpayers, in the case of ACA subsidiy eligibility) pays for half, working for insurance coverage wins.
But what if our couple just didn't pay the premiums, and paid those costs themselves; perhaps from a savings or retirement account. They'd eat the $31872.50 themselves without premiums, resulting in a deduction of $28337.50 ($31872.50 - $3,535) with a net tax savings of $4250.63.
In either of the two bottom cases, the difference if the couple were self-employed would be very small, because if one is self employed, you can deduct your medical expenses "above the line" before calculating FICA, and regardless of whether or not you use the standard deduction.
(
https://www.irs.gov/taxtopics/tc502.html)
I'm too tired to run those numbers at a 10% threshold, but I'm going to declare my own victory. From a purely tax perspective, the medical expenses deduction is better than the employment exemption for a 60 year old median couple with health problems. Of course, this is also super-simplified. The FIREd & self-employed couples can claim more expenses as medical deductions on their taxes than is considered against the employed couple's annual out-of-pocket limit; such as local or regional travel expenses, over-the-counter drugs, etc. It's also possible for either the plan to have a better negotiated price for cancer treatments, or for the FIREd couple to travel out of country for significantly reduced cash costs in a medical tourism region.