I think you'd be foolish not to charge for your time. You're known as an objective reviewer, which should go a long way for someone wanting just that, an objective review. There are lots of sites on the net with "reviews" posted by those receiving money from the camera manufacturer. The value of that type of review is questionable at best. There's truth in the old adage that "you get what you pay for". Richard
Adam's comment resonates. A smaller fee amount might make it easier to achieve volume, and the option to "vote with money" more than once would allow readers to express not just interest (yes/no) but also their degree of interest.
The more difficult part would be collecting --- the number of people who actually pay may vary dramatically from the number of people willing to click on a polldaddy.
Thanks for your great website first of all. I see two other solutions to your problem you might want to consider:
A) Set a cheaper price and get much more than just 100 buyers: your marginal cost is nil, thus you have a good chance to maximise your revenues by actually lowering the price you charge for the reviews. I for one would only consider paying $8 or more for a single review perhaps once per year if I am really considering to buy the the product. On the other hand I would pay $1-2 probably for every review published just out of curiosity. If you get 2000 or more buyers at $1-2 that's potentially even more rewarding than 100 or less at $15. What are your current hit rates for reviews? I could imagine a decent conversion rate of at a low enough price.
B) "premium" subscription model for the site with similar price of $1-2 per month to maximise subscribers. The premium content would clued all the reviews and perhaps more/higher-res pictures to your normal articles.
Where the revenue maximising price point lies for both models is of course unclear. It might be quite high with only few subscribers/buyers or it might be very low with a very high conversion rate from current readers. It seems to me that the low price/high subscr. model might be better suited to such content, but that of course is just a guess. It might be possible to experiment, although it can also be difficult to set a price point and then altering it radically. With single articles that might work best, I.e. write two reviews and offer one high and one low price and see what happens?
Personally I would definitely be in at $5. More than that would depend on a host of things.
I think it would be best to pick a fixed amount - say $5 - and then adjust the number of people paying based on the total cots. With an option for people to buy more than one "share" to increase their odds of winning, or help push a review they really want.