Just for another data point... I just finished the AOPA CFI refresher. Don't have to be an AOPA member to do it.
https://www.aopa.org/Pilot-Resources/Flight-Instructor-Resources/CFI-Renewal.aspx
$124 and about 4 hours later I'm done. You do 16 CBT modules. Each slide in those is timed for about 5 seconds before you can advance. Then there's a ridiculously easy quiz at the end of each module. When you're done, you submit one form to AOPA, another on IACRA, and they do the rest.
I chose them over American Flyers because that $124 includes them processing your paperwork for you. (Not driving to the FSDO is worth $$ to me.) I may or may not care about my CFI in 2 years, so the right-now-savings at AOPA was more important than the maybe-useful-maybe-not savings of AF in the future.
Anyway... fairly painless considering it's a CBT on steroids.