Some quick looking at Newegg, 4GB DDR3 1333 ECC DIMM, $33.99. 4GB DDR3 1333 Non-ECC DIMM, $21.99. Savings, $12. (Yes, I realize the Motherboard also needs some extra circuitry, I expect it's less than $1 in quantity though).
Pretty much everyone I know values their data at more than $12 if it is lost.
The problem is that if you want to move past the 4GB modules, things can get expensive. Bearing in mind the subject line, consider for example the completely awesome Intel Sandy Bridge E3-1230 with a board like the Supermicro X9SCL+-F, which can be built into a low power system that idles around 45W if you're careful. Problem is, the 8GB modules tend to cost an arm and a leg; http://www.google.com/products/catalog?q=MEM-DR380L-CL01-EU13&oe=utf-8&rls=org.mozilla:en-US:official&client=firefox-a&um=1&hl=en&bav=on.2,or.r_gc.r_pw.r_qf.,cf.osb&biw=1043&bih=976&ie=UTF-8&tbm=shop&cid=8556948603121267780&sa=X&ei=HxmMT5btB8_PgAfLs5TvCQ&ved=0CD8Q8wIwAA to outfit a machine with 32GB several months ago cost around *$400* per module, or $1600 for the machine, whereas the average cost for a 4GB module was only around $30. So then you start looking at the less expensive options. When the average going price for 8GB non-ECC modules is between $50 and $100, then you're "only" looking at a cost premium of $1200 for ECC. For $1200, I'm willing to at least consider non-ECC. You can infer from this message that I'm actually waiting for more reasonable ECC prices to show up; we're finally seeing somewhat more reasonable prices, but by that I mean "only" around $130/8GB. ... JG -- Joe Greco - sol.net Network Services - Milwaukee, WI - http://www.sol.net "We call it the 'one bite at the apple' rule. Give me one chance [and] then I won't contact you again." - Direct Marketing Ass'n position on e-mail spam(CNN) With 24 million small businesses in the US alone, that's way too many apples.