Here's a Price Comparison that I went to research. It is accurate as of 5 January 2020. However, due to the increase in popularity of film, Kodak and other brands have announced that they will be increasing their prices to cope with the demand, so be prepared to face increased prices in time to come.
Special Prices for Kodak Gold:
1) Fotohub only sells Kodak Gold for 24 exposures, so it is not very worth to pay 7 dollars just to get 24, when you could be paying 7.80 to get 36 exposures.
2) Standard Photo has discounts for the more packs you buy, so
- 1 roll by itself costs 9 dollars
- 2 rolls in a pack costs 17 dollars which is 8.5 dollars each
- 4 rolls in a pack costs 32 dollars which is 8 dollars each
Overall, it is cheaper to get the common films (Kodak Gold, Ultramax and Colourplus) from Filem, and their delivery fee is the cheapest ( if you don't opt for the more expensive $3+ Ninja Van delivery service). However, they have inflated their prices for Kodak Portra and multiple of their cameras are resold at way more expensive prices than the original.
These are the common shops that I know of, but there are definitely other options from Amazon (have to consider the delivery prices so ordering in bulk is cheaper) , and Carousell.
Kodak Portra is also generally cheaper when bought in packs of 5 from Amazon ( I managed to get a pack for Portra 400 where each roll is approx 12 dollars)