Hey, I'm in obscurity too. We should meet up some time. ... But it's pretty crowded here, we may have to book ahead to get two seats together.
I presume the costs you give are just the space rental, production of artwork to go up onto the board is going to add even more, yes?
I was inclined to agree with Cinisajoy about much of it ... but then look where I live. You probably have the population of Australia going past your proposed billboard every day. I'd have to teach kangaroos how to read to make it worth while here.
It would be an interesting experiment if you can afford it ... but I'm really not sure you can force your way out of obscurity like this.
The whole price thing is difficult to guess at. Yes, there are a lot of people that won't even look at a new indy author unless they can get the work free. (And a lot that won't even look then.) But there are also a lot of people that think "free" is a sign of worthless. My own opinion is that price, at the level that most indies charge, is of less importance than other forms of marketing. A few dollars is effectively nothing compared to asking the person to invest their time in reading your book.
We haven't seen VyderScope (Vincent Trigili) here for a while (more than three years), but when he was here he was a proponent of the "give away the first of the series" approach. Note, however, that he has a blog article up on his site now that speaks of a mammoth effort in which he got 6 books ready (doing right all those things he'd done wrong with this first books - getting professional editing and covers etc) and then released them over a tight schedule to keep his name up on the lists for an extended time. According to the article "that changed everything" (very much for the better).
An incredible effort, but even that may not have worked if he did not already have a collection of books in backlist and with generally good reviews. That is, if he hadn't already spent so long working to get where he was when he made that effort.
Hugh Howey, on his site, speaks of a break-out book: the book that finally gets enough attention that some sort of momentum builds up and things really start to happen. The implication being that success is not something that can be forced, but something that arrives as a sort of X-factor only after you've put in the work to make it possible.
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I'd say, if you were going to try this billboard thing, and you want to give it the best chance of doing something positive for you, then you need to align it with something significant in your publication schedule and other marketing. (The downside being that you will never know if it was the billboard that made the difference.
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