Let's take your info regarding the Yoga niche - I am thinking of making a main Word Press page myself and then build individual pages using software mentioned on your blog called "speedxxx" (can't remember full name 555) These pages can be quickly constructed and easily linked to each other via contextual links. Obviously making sure each page-product are closely related plus the normal traffic generation techniques, do you think this is a viable way to build an authority site Stuart and also overcome this idea that some Amazon products sell whereas some don't?
Anyway, my guess is that this site ranking at #8 in Google for this keyword and the high CPC, probably pulls in between $500 to $1000 per month. In fact it could actually be much more that that just depending on how much traffic they really receive. This is with the assumption that they receive traffic from more than just this keyword (which is the case with every single website I have ever owned).
Many affiliate programs will often run promotions with good discounts or giveaways that might be attractive to your audience. For example, if you're an Amazon Associate and the site have a big Holiday Sale, it would be the perfect opportunity for you to promote discounts to your website visitors. This is a great way to promote your offers while also providing good value to your audience.