Good afternoon and thank you for your question. First it would help to know what it is that you want to accomplish. To make the lines around your lip a litte less visible, Botox could be an option, however, there are other options that could be better for you such as Juvederm Volbella (hyaluronic acid dermal filler) that is specifically designed to smooth the appearance of vertical lip lines. You can also consider to add some volume and definition for the lips. To answer your question about the cost, Botox is between $14-16 per unit and Volbella around $450 per syringe, depending of the area and the injector expertise.
Pricing varies by location and injector experience. Typically, 4-8 units of Botox or an equivalent amount of Dysport is used to soften vertical lip lines and to slightly evert the lip. In my area, the pricing ranges from $12-17 per unit of Botox.