> $20k workstation, best case: $15k M5 Ultra 512GB, 36-month amortization, ~$440/mo. Runs a GLM-5.3-class model at ~30 tok/s. Saturated 24/7 it produces roughly 58M output tokens/month.

For agentic coding, ~90% of the cost comes from cached input tokens. This cost increases quadratically with the session length. If sessions go near 1M context, the number of cached input tokens can easily exceed 1B in a day.

GLM-5.3 @ $0.26/M x 1000 = $260/day

This is the math to use.