Jeff,
From the Certmetrics site "If you hold an A+, Security+, Linux+, Pen Test+ and or CySA+ and you plan to renew fully with a higher level CompTIA certification then your CE fees will be waived.".
I hold Sec+, CySA+, Linux+, Cloud+, and Data+ AND CASP+. I pay $50 for CASP+. That's all...