Need Help in dynamic JS generated Code while scraping a site

I'm a newbie to scraping. I'm trying to scrape the value from this site with button Buy Now.
Option I've tried is:

from PyQt4.QtGui import QApplication
from PyQt4.QtCore import QUrl
from PyQt4.QtWebKit import QWebPage

class Client(QWebPage):
    def __init__(self):
        self.app = QApplication(sys.argv)
        QWebPage.__init__(self)
        # self.loadFinished.connect(self.on_page_load)
        # self.mainFrame().load(QUrl(url))
        # self.app.exec_()
    def on_page_load(self):
        self.app.quit()
    def mypage(self, url):
        self.loadFinished.connect(self.on_page_load)
        self.mainFrame().load(QUrl(url))
        self.app.exec_()
client_response = Client()

def parse(url):                # OSRS + RS3
    client_response.mypage(url)
    source = client_response.mainFrame().toHtml()
    soup = BeautifulSoup(source, 'html.parser')
    osrs_text = soup.findAll('input', attrs={'type': 'number'})
    quantity = (osrs_text[0])['min']
    final = 0
    if(quantity == '1'):
        final_osrs = round(float(soup.findAll('span', attrs={'id':'goldprice'})[0].text),3)
        print(final_osrs)

    else:
        price = round(float(soup.findAll('span', attrs={'id':'goldprice'})[0].text),3)
        final_rs3 = price/int(quantity)
        print(final_rs3)

This approach is not good because it's taking too much time to scrape. I also tried Selenium Approach but that's also not needed at the moment.
Can u guys please suggest me the better way to scrape the value? . Any help will highly be appreciated. Thanks.

P.S: I tried this library because the content was dynamically generated.