Is it permissible to increase the price of an order by $5 after adding one extra rock to every 209 rocks priced at $1000, making the total 210 rocks for $1005? And is this action correct?

If the customer accepts the price increase in exchange for an increase in the number of items, or if it is their custom to accept, then there is no harm in that, as the condition of mutual consent between the two parties is met. However, if they do not accept, it is not permissible to increase the item in exchange for an additional payment. Rather, they must be given the choice between having it sent for the stated amount or having it removed from their allocated quantity. Allah Almighty says: (O you who have believed, do not consume one another's wealth unjustly but only [in lawful] trade by mutual consent.) And the Prophet, peace and blessings be upon him, said: (Indeed, selling is by mutual consent.) And a sale made under duress is not valid.