As a kid, I had a few of the Lego "Expert Builder" sets, so when the first Mindstorms kits came out, as an adult I was pretty stoked. I thought "here's a good

As a kid, I had a few of the Lego "Expert Builder" sets, so when the first Mindstorms kits came out, as an adult I was pretty stoked. I thought "here's a good way to prototype building robots and having fun too" - and I could use my old kit with it. I found that buying that first kit rather steep, but I persisted. Over time I purchased more parts, hit up the Lego-Pitsco-Dacta store to get others (stuff like pneumatic pieces and gears), and a few of the Mindstorms expansion sets... I sunk several hundred into it all before I came to realization that it wasn't cost effective; today I know it isn't. If you want to prototype (or outright build) robotic systems, just go with "raw" materials (especially surplus or junkyard pulls). Small scale stuff can be easily bodged together with hot glue, cardboard, and RC servos. At the time, a great controller for it all was the BASIC Stamp, today it would be an Arduino, RasPi, or ESP8266 - or any number of other options that are all low cost. Still - where Lego (and other building kits) shine is the modularity and standardness of the system. There have been attempts, some fairly successful, to do the same with more robust (mechanically and structurally) parts for kits (makerbeam, vex, actobotics), but they don't all have the traction the Lego enjoys from being a near first-mover, and not requiring tools to put together. But if you don't mind tools - there are plenty of lower cost options out there (not saying this because people don't know it - plenty do).