I think the price is important, because if it's too expensive people may choose cheaper books, especially as the bigger publishing houses are able to offer discounts more easily than self-published authors. Having said that, the price should really be in line with other books on the market as if it's priced too low, especially with a self-published books, people may think it's not very good. I think yours may be priced a bit too high at £13.30 (currently on Amazon UK) as most bestselling paperbacks are usually priced at around £7.99/£8.99 and are usually offered at a discount by the larger bookshops.