I think you are right about the costs.

Perhaps the pharmacy is assuming an injection once/month instead of once/week.

The attached pdf is from the Kaiser, and the Actemra cost does look like it is for a single injection. And the Kevzara cost I quoted was actually only for 2 injectsion With this understanding, costs look more like

Actemra = $4641/MONTH

Kevzara = $7853/MONTH

The $15,000 corporate offsets will not go far, about 3.2 months with Actemra and 1.9 month with Kevzara.

Or I could get shots bi-weekly and double these periods.

The studies I saw indicated this reduced effectiveness somewhat though - here's a some quotes from New England J of Medicine study on Actemra:

"A total of 56% of the patients in the group that received tocilizumab weekly and 53% of those in the group that received tocilizumab every other week had sustained remission at 52 weeks."

"The percentages of patients who had a flare were 23% in the group that received tocilizumab weekly, 26% in the group that received tocilizumab every other week"

"The mean increase (indicating clinical improvement) from baseline to week 52 in the SF-36 physical component summary score was 4.10 in the group that received tocilizumab weekly and 2.76 in the group that received tocilizumab every other week, whereas scores decreased (indicating a worse condition) in the two placebo groups..."