I've recently found that the price of Lego - at least on the used/second-hand market - has fallen, depending on what you are looking for.
Complete sets are still hella-expensive - especially vintage ones. Certain custom models can also be very expensive. Lego Mindstorms of the past two generations (NXT and EV3) are also still up there in price.
But bulk Mindstorms, Technic and Expert Builder are all still fairly cheap (just stay away from pneumatics - that stuff is still pricey for some reason).
I have found the Mindstorms RCX 1.0, 1.5, and 2.0 (aka - yellow programmable brick) are all fairly cheap. The touch and light sensors aren't too expensive, and the going price for the PB is around $30.00 USD. Rotation sensors can be up there sometimes, and the temperature sensor is hard to find and expensive. Motors are cheap though (the 9 volt block ones) - most can be had for around $15.00 each.
Bulk parts are similarly low cost. Even the NXT and EV3 motors and sensors are fairly inexpensive (not as cheap as the older RCX, but not crazy). Since they use standard interfaces and connections, they can be easily controlled using a Raspberry Pi or Arduino. The RCX takes a bit more work (you have to use an h-bridge for each motor, and sensors require an ADC; easy on the Arduino, but you need something external for the Pi).
The various Mindstorms "Vision Command" and similar cameras are also fairly cheap; they aren't anything special - very low-res (352x488 IIRC) web cameras in a Lego enclosure. But you can get them to work with Linux (you have to preload the
V4L1 library before executing a program like cheese or whatnot) - this used to not be the case (no driver existed about 8 or so years ago).
But yeah - if you're ok with hitting the second-hand market via Ebay or garage sales, you'll find it's now fairly cheap (again, staying away from things like the latest Mindstorms).
Oh! I also found that the Lego Dacta Control Lab (9751) interface can also be found cheaply - you can get 'em for $40-50 USD; they work with all the old 9V sensors and motors for the RCX. I've read that you can use a USB to DB9 serial port converter with them, and there is a ton of 3rd party libraries out there for control (I found ones in C, C#, Python, and Java).
> pneumatics - that stuff is still pricey for some reason
To hazard a guess, Lego's pneumatic sets tend to use just a couple pistons, while hobbyists buying the stuff want to do entire pneumatic-centric builds with many of them. Also the hoses break more often than other pieces.
Complete sets are still hella-expensive - especially vintage ones. Certain custom models can also be very expensive. Lego Mindstorms of the past two generations (NXT and EV3) are also still up there in price.
But bulk Mindstorms, Technic and Expert Builder are all still fairly cheap (just stay away from pneumatics - that stuff is still pricey for some reason).
I have found the Mindstorms RCX 1.0, 1.5, and 2.0 (aka - yellow programmable brick) are all fairly cheap. The touch and light sensors aren't too expensive, and the going price for the PB is around $30.00 USD. Rotation sensors can be up there sometimes, and the temperature sensor is hard to find and expensive. Motors are cheap though (the 9 volt block ones) - most can be had for around $15.00 each.
Bulk parts are similarly low cost. Even the NXT and EV3 motors and sensors are fairly inexpensive (not as cheap as the older RCX, but not crazy). Since they use standard interfaces and connections, they can be easily controlled using a Raspberry Pi or Arduino. The RCX takes a bit more work (you have to use an h-bridge for each motor, and sensors require an ADC; easy on the Arduino, but you need something external for the Pi).
The various Mindstorms "Vision Command" and similar cameras are also fairly cheap; they aren't anything special - very low-res (352x488 IIRC) web cameras in a Lego enclosure. But you can get them to work with Linux (you have to preload the V4L1 library before executing a program like cheese or whatnot) - this used to not be the case (no driver existed about 8 or so years ago).
But yeah - if you're ok with hitting the second-hand market via Ebay or garage sales, you'll find it's now fairly cheap (again, staying away from things like the latest Mindstorms).
Oh! I also found that the Lego Dacta Control Lab (9751) interface can also be found cheaply - you can get 'em for $40-50 USD; they work with all the old 9V sensors and motors for the RCX. I've read that you can use a USB to DB9 serial port converter with them, and there is a ton of 3rd party libraries out there for control (I found ones in C, C#, Python, and Java).