Writing script

Good afternoon, web programmer services are required. We need to write a parser script. The script is needed for dumping prices on the site. Here's a product on the site. Our store is at 3rd place. And the parser should make the price 1 unit cheaper than the seller, who is in first place. Then he loads the price onto the set.
I am interested in the cost of writing a script and timing. Having a portfolio is mandatory.