I suspect that a proportion of testers are lenient in their reviews and marks out of ten because they haven't spent their own money on the products ( there is a handling fee paid by the tester, so not completely free). I'm the opposite (probably why I've never been quoted in the books!) and there's a final question on the lengthy questionnaires for each item which asks "would you repurchase? Y/N?" If a product is lovely and gives some improvement but costs >£100 I'll still say I won't repurchase. Given the wording "would you?" it's possible to answer this with a "yes, I would repurchase...if it were half the price" It's conditional question open to interpretation. IMHO the question should be "Will you buy it again?"
So i've read the green BB most recently and enjoy the explanation of the products and comments may tempt me to try something new, the marks out of 10 have less relevance as the groups are small, any extreme marks that deviate from the average can skew the results. It's still more interesting to read the contributors' reviews than just the opinion of Jo Fairley, Paula Begoun or other self-appointed expert.
Jude xx