How practical is it to convert one element to another using a neutron source?

I understand this is indeed done at times. I believe that Bismuth can be converted to Polonium when bombarded by a neutron source. On the other hand, it appears clear that neutron sources aren't exactly the Philosopher's Stone, currently. We don't seem to be able to convert lead to gold cheaply, en masse, using neutron sources, for example. If so, gold would be a lot cheaper than it is, obviously. So, what exactly are the limits of our abilities to use neutron sources to convert one element to another? How expensive is it? How dangerous is it? How practical is it, in general? Are there any approaches which might make the neutron source more closely approximate the Alchemist's ideal, the Philosopher's Stone -- not just to convert lead into gold, but any element into any other element we choose, cheaply, and in large quantities? Thoughts?