I guess I better preface my comment with, my mother always told me "I had more money than brains" haha
I have been using Infinity's uppercase Designer set ($210.00) infinitystamps.com/oscommerce/product_info.php?products_id=163 for almost 2 years and they still are making a very nice impression, no signs of wear yet. For the most part I believe in the old adage "you get what you pay for." With the infinity stamps it's not only the quality of the hardening process but also the sharpness and angle of the imprint the stamp is made at. As I recall I was told that the stamps should be good for about 4000-5000 impressions when solely used on stainless, 8000 otherwise. You can discuss that with Infinity before ordering your stamps.
Bottom-line, lower initial stamp investment does not necessarily mean best overall cost effectiveness or value.
Well that's my 2 cents :-)
Hope everyone has an enjoyable weekend!