Yes $99.95/ea. but you get what you pay for.
1.Motion with adjustable parameters
2.Secure protocol and reliable 2 way communication.
3.Light sensor with precise level indication through homeseer.(For those that wish to use it)
4.Temperature sensor with an accuracy of 0.2F with live temp. reading in Homeseer.(Again Homeseer also supports X-10 and has many users in HA community of DIY or not).
5.Has real time battery monitor with alert level set by user.(Alert at 30% or 50% etc,...)
6.300 foot range but I'll be happy even with half of that.(Try that with a CM15A unless you hack it with antenna as many including myself have done---Non FCC conform)
and so on .......
Yes MS10A get them for $10 + shipping(bundled deals) but not secure(easily disables with constant remote press) or using ext code in AHP.
Data collision makes them unreliable 50% of the time and range is at best 50ft. unless CM15A hacked or use WGL units/RFXCOM.
No battery monitor,no 2 way comm,45 second fixed delay before it resets but hey you're right at $10 bucks it's a steal.
As time goes by most HA geeks and automation enthusiasts will want more than to putz around and get into reliable,secure and headache free Home Control.
X-10 is a great deal for the money but create a shopping list X-10 vs ZWave or Insteon and what really is the price vs value advantage.Oranges and apples.
X10 good to have fun and non-critical applications .... ZWave,Insteon(yes they have good points) reliable and the future of HA.
IMHO of course and if anyone can bring up other interesting points please do ...hence the beauty of this open and friendly forum.
Thanks for the input Dave_x10_L it would great to get debates going,very good points can be made in every direction.Many questions could be answered.