Your point is not unfounded, and it's our duty as research scientists to justify the value you receive for your money.
There's a famous example where a US Senator asked a similar question of a research physicist prior to the establishment of Fermilab, specifically tailored toward defense application [1].
SENATOR PASTORE. Is there anything here that projects us in a position of being competitive with the Russians, with regard to this race?
DR. WILSON. Only from a long-range point of view, of a developing technology. Otherwise, it has to do with: Are we good painters, good sculptors, great poets? I mean all the things that we really venerate and honor in our country and are patriotic about.
In that sense, this new knowledge has all to do with honor and country but it has nothing to do directly with defending our country except to help make it worth defending.
To address your concerns more directly: Basic and exploratory research pushes scientists to extract the very highest performance one can get from known technology. On occasion, that technology can do something exceptional (precision timekeeping, GPS, vaccines, medical imaging, etc.). The highly-motivated people who do this work tend to be willing to do it at low salaries and with limited chance for advancement, simply because they love the field. You can think of it as a low-cost government-run VC fund that aims for the occasional spectacular payoff at multi-decade timescales.
Another key benefit is education: research funding underpins the post-graduate education of most people in the physical scientists. Funding basic research, which companies won't usually touch, furthers the continuous supply of a top-notch skilled workforce for industry nationwide.
Furthermore, in many fields, retaining a trained and knowledgeable corps of scientists is an efficient way to retain the capability to respond to sudden and important societal needs (Manhattan Project, Ebola, asteroid mitigation, Fukushima, etc.).
I'm biased, as taxpayer dollars pay for my work, but I think you're getting a reasonable-to-excellent return on your investment.
[1] http://history.fnal.gov/testimony.html