Questions:

Do you know of a better/cheaper product, yet pitch the costlier one?

Do you believe the product in question will be harmful to your audience?

Are you mis-representing the value or impact of the product?

These are important questions to answer before you make a choice to keep
promoting it.

encsteph has a GREAT question affiliate marketers can ask themselves
when sufficient expertise is gained in a niche, and you're looking to
create your own product or service...

Would it be possible for you to create your own product in the same niche?
Thereby alleviating all of your ethical concerns and potentially making
you more profit since you get it to keep it all.
constance said:

I'm seeking an honest path in this business and it's not always easy.
That's so true. But stick to it, and you'll be around for a long time
with your reputation intact. In the 13 years since I've been working
online, I've seen barely 2% to 3% of those who started with me still
around with their good name and authority untarnished.

It is often tough to say 'No' to $700+ commissions. But on the few
occasions where I have promoted a product without knowing the background,
carried away by the commissions alone, I have ALWAYS regretted it - and
felt like a cheat who misguided people who trusted my judgement.

Jay Abraham, my business mentor and guide, has a principle called "The
Strategy of Pre-Eminence", which distills down to putting your client
first, and being seen by your audience as the only viable solution to
any problem.

You can't do that while driven purely by profit at the cost of all else.

This note I shared with my email subscribers sometime in 2006 is still
relevant as a kind of touchstone for affiliate marketers who care about
ethics and values:

http://www.ezinemarketingcenter.com/why-email.htm

All success
Dr.Mani

P.S. - In case this comes off as sounding "holier than thou", I'll confess
that in the earlier days, I too have spammed, promoted shady stuff, and
gone after the juicy commissions - but the lesson I learned is that while
such behavior IS profitable in the short-term, it is seriously damaging
to your long term reputation.

So, if you intend sticking around this game for long, it pays to be fair
and focus on delivering value first.

My 2 cents