The problem is not the budget. In real life you can do a lot of things with 15 billion dollars a year.
NASA does do a lot of things with their budget. The problem is, we're asking NASA to return Platinum Card results on a food stamps budget. They don't just build spacecraft, you know. They operate a global system of satellites to monitor the Earth, they run telescopes, they do cutting edge research on aircraft design, materials research, medical research, you name it, NASA's researching it. Some of those programs would be better served, I'm sure, by having somebody else research them, but NASA can't always pick and choose what they get to spend their money on Congress does a lot of that for them.
This could be said about almost most things various interest groups desire. I'd like to see $15 billion spent on urban rail transit every year, you'd like it to go to NASA, I'm sure some guy like Tex would favor spending it on hookers and blow. But before long, we run out of all those $15 billion pots.
Actually, $15 billion would be a reduction of NASA's budget. Its averaged, unadjusted for inflation, at around $20 billion/yr since the Apollo era.
Venusian surface rocks &/or other surface material(s) would be very interesting to study, as would underground material(s), perhaps, probably if not moreso!
