Coinbase Recurrent Purchase - They are likely scamming you

I buy Bitcoin every week through Coinbase using their recurrent purchase feature, and once it's available, I withdraw to my HW wallet.

I have been noticing how Coinbase always picks a price that's on the top 10% prices during that day as the sale price. With an example, if the price for a given day ranges between 50K and 52K, you will almost certainly get an auto-purchase sale price of ~$51,900.

Yesterday's case is more egregious. Besides the $3 fee applied, they gave me a sales price of $67,022.51 / BTC - a price that was never reached in their platform.

It's pretty obvious to me that they are scamming me, and probably everybody, with the sale price. In between the fee, and the inflated price, I think they are regularly making 5+% on each of my purchases.