It depends. Lots of variables to consider.
Do you want to purchase a ready made cage (NOT one from a pet store, it won't be large enough), or build your own (see the Main tab at the top of the page and the photo galleries for examples)?
How many pigs are you talking about (two, I hope, as they're herd animals and do much better with a buddy).
Good quality hay will run you about $50-$70 every five to six months if you buy it online, or about $1.75 a pound. If you can find local grass hay, it will be much cheaper, $10-$20 for a whole bale. Hay from a pet store will be poorer quality and will cost $3-$5 a pound. Two pigs will eat 5-8 pounds of hay a month.
A good quality pellet (Oxbow and KMS Hayloft are the only ones we recommend) will be about $30 every six months.
Vegetables vary widely depending on the time of year, but I spend $10-$12 per week for three pigs.
The BIG expense is vet bills. Small animal (dog and cat) vets are not qualified to treat guinea pigs, and some are downright dangerous. You'll need a good exotic vet -- they're scarce and usually fairly expensive.
I use wood pellets covered with fleece for bedding. The pellets are about $7 per bag, and I use two bags about every three months. Fleece can be as cheap as $2-$3 for a throw from Walmart or Target, or several dollars a hard for cute stuff from a fabric store. It's been years since I've used aspen, and I've never used Carefresh, so someone else will have to comment on that.
Here's some reading material for you before you actually get pigs:
https://www.guineapigcages.com/forum/threads/113176-Information-for-new-guinea-pig-owners and
https://www.guineapigcages.com/forum/threads/107827-What-NOT-to-do-for-your-guinea-pigs!