A given town has limits on how much it can increase the size of its measures. If the rationale is to avoid inflation, then why increase at all? Perhaps it's a concern of "ona'ah" - defrauding either party - but the Gemara rejects that as a concern too. And so on, for a few attempts. Plus, the use of verses to establish the adjustments to weights and measures. Also, people who hold onto produce as a matter of hoarding, usurers, and those who mess with their weights and measures - all of whom are treated by the law as not great, deceitful categories of people. Plus, a differences in marketplace practices by Shmuel and his father, to make sure the price there isn't driven up.