There's no set shipping price for Saudi Arabia on the site. What you pay varies with the courier and where you live, and checkout shows it before you place the order. Bulky or heavy parcels can carry an extra charge, so get in touch with the store before ordering them.
Free shipping is a promotion that runs only at certain times. According to the FAQ, some countries get it once the cart passes a minimum listed on the site, yet Saudi Arabia has no published figure, so look at your own cart. Any product whose page lacks the “Free delivery” label doesn't qualify, and neither does anything on clearance. Mix those items with free-delivery ones and shipping is added, which you'll spot at checkout.
Customs or clearance charges on parcels sent outside the UAE fall on the person receiving them, per the shipping page. Where Saudi orders are dispatched from isn't stated, so for a big order, check with customer service beforehand.
Source: Dr. Nutrition Saudi Arabia: shipping and delivery