There is real and percieved value. There is value proved from trying out a product first and seeing that it works for you - versus buying it on a "guarantee".
I've often held - and work from - the idea that economics is based on the exchange of valuables in order to improve one's quality of life, one's standard of living.
"Shlock" (cheap, coarse) products get only a small amount of money from a person for 97% of the buying public. 3% will buy whatever you have, regardless of quality.
I work in a warehouse (day job) moving boxes around full of furniture mostly made in China. I used to do Quality Control there, inspecting stuff when it came in. So I know that the bulk of the stuff we sell and ship out is of dubious quality - great for our throw-away society, but nothing that is going to be handed down as any heirloom. The phrase we often recount as we find out what the customer has paid in price and shipping, "More money than brains."
I don't know how much customer turnover we have. I've had my own experiences in buying (one of the few) decent products from this place and then having waits and even the wrong item shipped to me. But that was years ago - and I still won't buy anything unless it is on a severe discount and I can see the product first.
So when I open a sales page and it says "guaranteed to raise your email response rate" I know it's another "made in China" situation. Great for the "masses" (those 3% with fatter wallets than craniums), but for the rest of us - we're better off not.
A little more study and comparison will bring a lot of this data to you. Or simply go to a brick-and-mortar store and start leafing through the actual books. Google Books and Amazon previews also provide this service on a virtual basis - you can read nearly or all of the books in this fashion, thought it isn't as rewarding as leafing through the actual.
I would say, then, to go the Lulu route where you can offer up a preview online - even setting the entire book up as a preview. People can't copy it, so they can simply get the data and then pay for a download or printed version when they see the actual.
Go ahead, kick a few tires before you buy - look under the hood, smell the upholstery, check out the carpet, look in the trunk, take out the emergency jack to see how it works.
This really comes as I have been reviewing a product I bought (one of those "$47" funnel products) which has turned out to be really inferior. And I cancelled that subscription. That guy is selling shlock. The system for sales works and works. Because he has amassed a ten or twenty thousand names, he can make consistent money off the 300 or 600 people who will buy anything he comes out with. And these people simply stay on his list and keep buying.
I did a study some time ago on a corporation which lost 80% of its new customers in the first three years. And within 10 years, it had lost all but 4-5% of the original customers. It had amazing customer turnover. Yet it was still making money hand over fist, since that small amount of "more money than brains" customers were kept on and played to. The corporation has been shrinking, slowly, for over a decade. Really because it has such a pitifully poor conversion rate - it just doesn't produce a quality product that is widely useful to helping people improve their lives.
Since this company makes more money from the upper end of its product funnel, they spend the bulk of their time catering to these few big spenders, and not to sorting out how to get more people in at the introductory levels in order to get more big spenders in for their upper level services. They simply keep coming out with more and more products these "more money than brains" percentage will buy. That company doesn't take a percentage of that income and then invest it in surveys and studies and products which will convert people in greater volume up their sales funnel.
In short, they don't really service their public, they just keep working the percentages. They have a con game going on of sorts. And that company's reputation is shot, with numerous "anti-" websites and blogs who do nothing but simply flame that company with every post.
Instead of introductory service research, that company spends its money on lawyers and "PR" to "combat" these people on the Internet - which is about as fruitful as standing in a flowing river and trying to blow a leaf back upstream with only your mouth. Could be done, I suppose...
I found the same problem with two "make money through mailing lists" people. Both simply made most of their money through personal coaching. Again, they were selling to the already converted and mostly running a percentage game instead of really producing value that could improve someone's life.
So, keep your funnel wide at the bottom. Lots of entry points. And then constantly survey those niche publics for what they really want and why they bought what they did. Work consistently on your conversion efforts - make sure what you are selling people is actually helping them. If you do this well, you will get people who do more than just buy your goods - they will start being active evangelists for your cause, working for affiliate fees and helping you with your conversion and quality issues.
But quality - real value - of product is where you must focus the bulk of your efforts. You can always hire someone to help you with investing the extra money you recieve in return. But you are on this planet for such a short time - don't waste it accumulating some paltry sums when you could be helping hundreds of thousands (and perhaps millions) improve their lives.