The BJ's path beats this at >7%.
The bigger problem is that the 6% benefit on Blue Cash Preferred caps out at $6,000 per year and if you're hitting that limit with organic grocery spend anyways, you're just trading real grocery rewards for gift card rewards. Then you need to use a card with lower earning power for all of your grocery spend >$6,000.
Your example is assuming that BJ's cards are on sale.
I agree and have pointed out many times that you can certainly come out ahead over Target's 5% if you buy cards at BJ's or Sam's and have a card that earns at least 1.5% back.
If we look at normal prices BJ's is 4% on the $500 cards ($479.99) and a 2% card nets you $9.60 and takes the price down to $470.39 which comes out to 5.92%
If we buy a card at any grocery store with the AMEX BCP we would pay $500 but get $30 back bringing the cost down to $470 which of course is 6%
If you factor in grocery stores that give fuel points for your purchases you can certainly add to savings.
Kroger owned stores offer a fuel savings program that allows you to accrue and redeem fuel points.
Every $1 you earn counts as 1 point but Disney and other gift card purchases are multiplied routinely by 2x and very often have 4x fuel point promotions.
Every 100 points will allow you to save $0.10 per gallon up to a maximum of 35 gallons.
Kroger allows you to combine your points to save up to $1 per gallon if you have enough points.
With the $500 card you would earn either 1,000 or 2,000 fuel points which would be valid for 1 or 2 fill ups of up to 35 gallons or $35 saved.
With a car that only has a 10 gallon tank and just the normal 2x on gift cards we would be saving another $10 in gas.
This takes the $500 BCP card down to $460 which is 8% off.
If you are able to utilize all of the 35 gallons then that would drop your costs down to $435 or 13% off.
You could then of course use a cc that gets a better percent back when purchasing the gas.
You mentioned that the BCP caps out at $6,000 and while that is true the original poster,
@muppets3d didn't specify how much in GC was needed so I think
@VGCgroupie suggestion of the AMEX BCP is certainly a good one as there really aren't any hoops to jump through and grocery stores are available pretty much everywhere where Target's and BJ's are not. Yes I realize you can order online but sometimes Target places a limit on the cards online.