Well, I understand your reasoning; but now a days there are laws protecting our beaches. I know what would a few pounds be in regards to the whole beach, but I would hate to see law enforcement catch you in the act and there be a law. You could find yourself paying a lot of money for logic! You also have to worry about contaminants. People throw a lot of CRAP onto our beaches. We all are faced with the same problem (prices for this hobby) and nobody said this hobby was cheap. One other option for you would be silicate sand (play sand), it must be pure silicate; but it can be purchased at Home Depot relatively cheap.
Just my 2 cents!