thanks .. one final point -
In case there were any other readers as stupid as me and thought you meant $500 million was at imminent risk of being wasted on SETI, that point has been clarified. Thanks.
not necessarily stupid, just not reading carefully enough. I usually take a lot of time & effort to understand things, and only in my 40s did I begin to feel I was getting any good at physics or anything else, for that matter. I'm a late-developer but am still winning due to the concentration and endurance I can bring to a topic. That's what counts, and it can be developed too, with desire ..
all the best.