Here is my research a year ago about pellets. The prices might have gone up slightly since but its a close estimate...
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25lbs timothy pellets $16 + 23.90 for shipping = 39.90
50lbs timothy pellets $28.50 + 29.97 for shipping = 58.47
Kleenmama's Hayloft
10017 N Coulee Hite Br. Rd
Reardan, WA 99029
Small Pet guinea pig food: Oxbow Essentials Food
Oxbow from defostersmith.com
Cavy cuisine pellets 50lbs 74.99 + free ship for over $50 = 74.99
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Sweet meadow timothy pellets
50 lbs $22.99 + 37.13 for shipping = $60.12
PetStupid online:
Oxbow pellet
10x5lb bags = $139.99 + $5.99 the cost of shipping = 145.98
Also shipping costs are based on my address which is in Minnesota (right in the middle of the 3 companies) If you live closer to one than the shipping will also be more or less.
But based on the 50lb price KMs is cheaper and since it is the best it is a win win situation.
How much you order is also based on how many guinea pigs you have. If you have 2 guinea pigs that are over 6 months of age they need 1/8th of a cup of pellets a day each. A week that is 1.75 cups. 1 lb of pellets is 2 1/3 cups so thats 3/4 of a lb of pellets per week. KM recommends keeping the pellets in a cool dark dry place (I keep mine in a standing freezer since I have bug and storage issues but you don't have to. She also recommends not buying more than a 6 month supply because she cannot ensure that the Vit C will be stable for more than 6 months. SOO based on that 26lbs will last you 6 months. So I would recommend buying the 25lb bag and replacing it every 5 months so that you can combine some of the old with the new the last few weeks and you are sure that you have a steady supply...
KMs is DEFINATELY worth it believe me in the gas and time alone its a great saver!!!
Good luck. Can't wait to see pics of those piggies enjoying those great pellets!