It depends. If this is some open technology, then it's rarely worth it - and I would definitely expect my developers to get proficient on their own. But there

It depends. If this is some open technology, then it's rarely worth it - and I would definitely expect my developers to get proficient on their own. But there are other, closed technologies, where such trainings can be useful. From the top of my head different Xilinx trainings come to my mind - they are pretty expensive, but they are rarely wasted money. As a counter example, I have seen some trainings from Actimize (closed source bank-related thingies). My colleagues were very happy with them, but personally I didn't get much more out of it than what's already in the PDF manual...