In the Outer has a post about Marketplace Ethics, Part I. I don't think this is about ethics, I think it is about wise dealing.

Customers pay for value received.

If another company can provide the same value that you provide at half the cost then you need to examine your business model and figure out a better way of providing that value.

If a competitor cuts the price because they are not providing value then its not wise for you try and match that price because your company depends upon the profitability of your business model.

Good customers appreciate value.

Wise customers know that you get what you pay for. So if you pay a cut throat price, you get shoddy value and poor service.

I say, if you have priced your product appropriately based upon the value you provide than stick to your guns when customers come shopping.

Proverbs 20:14 states "Utterly worthless!" says the buyer as he haggles over the price. But afterwards he brags about his bargain! (Living Bible version)

Or

The shopper says, "That's junk--I'll take it off your hands,"  then goes off boasting of the bargain. (The Message)

For a biblical perspective on marketing and other ideas for wise business dealing check out my series on Planning A Successful Small Business.

With respect to the issue at hand check out my third principle of Marketing for Success (Whatever is right is just and whatever is just is fair.) in the article:Conduct Becoming of a Christian in Business - Marketing for Success