Bargain what? Voyager had absolutely nothing to offer that wouldn't radically change the economy in which the Malons live by...
See Season 5 "Night" again. Voyager's crew offered Controller Emck, the Malon encountered in that episode recycling technology that would allow the Malon people to recycle their antimatter waste products, making it unnecessary for the Malon to dump it on other planets or in space.
The Malon controller however refused as while this technology would be a boon for the Malon civilization it would render the jobs controllers like him were performing (transporting and dumping industrial antimatter waste) obsolete.
So it is not that Voyager's crew had nothing to offer, Malon controllers do not want their civilization to acquire antimatter waste recycling technology.