For the Siglent SDS1104X-E, I can go directly to Siglent. Their price is the same as everyone else. The only reason I might not buy direct is if they don't have stock, or charge a high shipping fee. I would hope that buying direct from the OEM would guarantee that no "hanky-panky" has been going on with returned goods.
I personally will not use a 30-day return policy to "try out" a product. I always spend a lot of time (and over-thinking) researching before making a major (or sometimes even a minor) purchase. The only time I will return an item is if it is defective/damaged, or if it is obvious that the item had been previously opened and used.