This is a common question, especially for smaller companies, whose resources are limited. It’s certainly understandable for a manager to want to develop an incentive plan that only pays out of the company profits (if there are any).
No caps. We rarely recommend a sales comp plan be capped – no need to take your top performers’ motivation out. But we do recommend deceleration at high levels of attainment, per-deal caps, caps on the % of margin on a deal that may be paid to the rep, etc. – these keep pay rational…
We generally recommend that rates decrease at a very high level of performance, well above goal. And the decrease should continue to hold the rate above the “base rate” (immediately below goal rate).