Build the model over a defined horizon
Choose a horizon — commonly three or five years — and hold every option to the same one. Comparing a five-year service package against a one-year warranty without normalizing the horizon produces a misleading result.
The forgotten line items
Delivery and rigging. Electrical work and room preparation. Initial and replacement training. Consumables and accessories per session. Software or subscription fees. Extended service contracts. Calibration and preventive maintenance. Insurance. Decommissioning or trade-in value at the end of the horizon.
Price downtime explicitly
Estimate the revenue value of one day of unavailability and multiply it by realistic annual downtime under each service scenario. This single line frequently reverses a decision based on purchase price alone.
Separate utilization assumptions from cost
Keep cost modeling and demand modeling in separate tabs. Cost is largely knowable and verifiable; utilization is an assumption owned by your operation. Mixing them hides which number is actually driving the result.