• CPM is Cost-Per-Page-Impression. If your ad is presented to the browser, your account is debited this amount.
  (This is an important number in your Top-Search strategy. See formula information below.
   
• CPC is Cost-Per-Click-Through. When browser clicks through to your URL, your account is debited this amount.
  See below.

Search return positioning is determined by a rank factor which is the numerical sum of:  CPM x 30 + CPC.
This is not a cost formula, only a positioning factor calculation. Examples:

CPM	CPC	Factor	Positioning Rank
.10	.25	3.25	4
.11	.25	3.55	2
.10	.35	3.35	3
.11	.50	3.80	1

What are your priorities?
Low inventory on certain items but still want your name presented to the industry? Keep the keyword ad active with default CPM and CPC.

Loaded on some items and need to move-em out? Bid higher on CPM and up the CPC.

If you don't have a web under your control, get one under your control. The real objective here is to get a click through to your product offering focused web page with price or, to your ads or your specific ad at WDM.

A wise marketing person once said: "Money overspent on advertising can never be recovered." Avoid the same header in all keyword ads. If a click through or a certain product is a high priority, edit the header for better click through yield and bid higher for search return position. Be innovative, sometimes it's the innovative header that produces the click, not necessarily the search return positioning.