You are right in that the common user or every day user does not need a lot of accuracy as long as they understand that our cheapest model, the ParaZapper 6-Pack is guaranteed to be more than twice as accurate as the meter that you mentioned. Therefore, if there is any discrepancy, the meter is likely at fault.
Otherwise, yes, if someone wants to check "close", I agree with you that many cheap meters will do.
That aside, our customers should be highly satisfied that we use such high quality equipment to check our zappers.