The GPU Decision Matrix
On-prem GPUs: $30K-$200K upfront, low marginal cost, 18-24 month payback. Cloud GPUs: $0 upfront, $2-4/hr for A100, instant scaling. Spot instances: 60-70% cheaper but unreliable.
Rules of thumb: If utilization <40%, cloud wins. If >70%, on-prem wins. 40-70% is the gray zone where hybrid makes sense. Always model 18-month TCO, not monthly cost.