So you sell Cartell and think its the best - no problem with that. Not sure where you got the $40 figure. The one I am referring to costs about $130 for the 50' cable version and more for longer cables. I agree it doesn't have any timing adjustments but for many applications that isn't needed. The cartel has an additional relay in the control box so that offers a bit of isolation from lightening. That could easily be done with other probes by the installer but would need a few extra parts.
For anyone interested heres a link to a Cartell manual:
http://cartell.com/pdf/manuals/ct2b_m.pdf