Is there a way to get my husband and his son back to the united states if he lost his US residency for being out of the country for almost four years?

If the only reason that your husband and his minor son are unable to return to the US is because they have been out of the US for 4 years, this can be resolved, and it should not cost $10,000.  The only concern I have is whether this is the only reason he is being denied permission to come back.  The facts as you reported them are a little confusing, you indicate that they cannot come back because of their residency status, but at the same time you indicate that they have "valid green cards."  Permanent residence generally is deemed abandoned (and therefore lost) if the person remans out of the US for a period of 1 year or more.  They have been out for 4.  It may be that they may need to reimmigrate, I don't know if you are a citizen, but if you are, you could file for them.  I am also a little concerned with the malaria issue, but would first need to research whether Malaria is on the list of diseases that bar entry and require a waiver.  If you would like to discuss the particulars of this, please feel free to call my office at (619) 291-1112. Sincerely, Jan Joseph Bejar, Esq. For: JAN JOSEPH BEJAR, A Professional Law Corporation