I found a really good price on Amazon once and bought so many that I've never had to purchase them again (I have an older fridge so they're harder to find). It's been 6 years, lol.
I believe I saw Home Depot was now carrying their HDX brand in water filters for some models. Havent bought a filter in a while but would guess the HDX brand is lower cost than the oem filter.
Check reviews the one for my fridge stated it worked for half the number of gallons that the "official" one does. So the cost of 2 was greater than one of mine. Hope that makes sense.
I found them on Amazon for less than Home Depot or Lowes. And I signed up for automatic shipment as it made it even less. They ship one every six months, but email you when the next shipment is close so you have a chance to cancel that next shipment. I had read comments that some places sell ones that last only last half as long too and was concerned about it, but so far they have all lasted at least as long as the original and one from Home Depot did. Just keep an eye on the price as it does fluctuate from order to order. So far they have always still been less than what I would pay at Home Depot.
We buy ours from fridgefilters.com. It's been a while since we needed to buy because we stocked up last time but they have a "damaged box" special that knocks $5 off. Nothing wrong with the filter itself so that's what we get.
I'll have to compare with Amazon. We buy a lot of stuff there, belong to Prime, and love their subscribe & save plan.