Sorry, I was under the impression you wanted the cheapest single stick to post the system and that is $40. For more ram to run the best price is $50 for 2Gb kingston ram or $97 for 4Gb (2x2).
http://www.newegg.com/Product/ProductList.aspx?Submit=ENE&N=100007952+600006098+600006165+600006042&QksAutoSuggestion=&ShowDeactivatedMark=False&Configurator=&IsNodeId=1&Subcategory=541&description=&hisInDesc=&Ntk=&CFG=&SpeTabStoreType=&AdvancedSearch=1&srchInDesc=