Cost per token is a bit misleading because, as others have noted, different models use tokens in different ways. (Aside - This is also why TPS isn't a great metric).
We found that 5.5 is about 1.5-2x more expensive overall. On a "Pareto" basis, we only find 5.5 xhigh worth it. At the lower reasoning levels, 5.4 still edges it out on cost/perf.
We take a spec-driven approach and mostly work in TS (on product development), so if you use a more steer-y approach, or work in a different domain, YMMV.