What innovation made it possible to sell a lot of goods really cheap?

The innovation which made it possible to sell a lot of goods for very cheap is assembly-line production. THE ANSWER IS ASSEMLY-LINE PRODUCTION

in contrast, the biological controls are self-sustaining, inexpensive and very effective once established. biological control could be used on thousands of golf course acres, improving their biodiversity and quality as wildlife habitat. in the process, the golf industry will be shown to be leaders in an environmental stewardship program of benefit not only to the lands they manage but also to the watersheds in which they exist.

c. troops marched forward in close formation against newer, more accurate weapons