Client pressuring me to guarantee specific savings amount

Louisville restaurant chain wants me to guarantee $50,000 annual savings before they sign contract. I've done preliminary review and think $30-40k is realistic with LG&E. Should I guarantee the higher amount to get the business?

Never guarantee specific amounts. Too many variables outside your control. I offer "no savings, no fee" but never guarantee dollar amounts.

Thanks Marcus. That makes sense. I'll stick with contingency fee structure but no guarantees on amounts.