I don't want to sound negative, but attending that radio interview has a cost. I would say that arranging, preparing, and conducting a 10-minute interview still costs a half day of time.

Will the book sales from that interview justify that interview?

For my writing project, attending the right kind of conferences would help get my idea out there. But the fees, travel expenses, and opportunity costs are quite prohibitive.

Much cheaper to splash things on the internet. Maybe some luck will come my way.

I think the small self publishers are playing a numbers game. One successful writers can pay for the investment in 20 or more other writers.

If a small publisher approaches me and my unique topic, I would see that as a sign that they are ready to market my ideas.