Being a farmer I had to chime in on this one. It isn't true that farmers can't afford the expensive harvesting equipment. Some farmers do not own their combines (Harvester), but most do where I live. However, most farmers around here grow wheat as well as soys, corn (possibly dry beans of many types). Also, washing your combine or a heavy rain is not going to wash away all of the wheat. The wheat runs through inside of the machine and water can't get to all of the parts the grains touch. It is very true if something is harvested on the same machine as wheat there is NO way to guarantee it isn't contaminated. However, the combine is not the only problem, storage bins and trucks used to haul the grains are used by both wheat and other grains. I don't believe cross contamination is the only factor in not eating grains, but you are correct to worry about this.