Can someone help me figure out correct FBA Fees?

I recently started selling and have a product selling for $5.99. It’s getting popular, but the FBA fees are killing me and are nearly 70%.

Package is 9.5 x 3.5 x 1 and weighs 0.09 ounces.

When I do the FBA calculation I get 33.25 (9.5 x 3.5 x 1) and the divide by 139 to get $0.24 cents per package. On top of the 15% referral fee of $0.90 I get a total of $1.14 per unit.

My FBA fee is showing as $3.31, for a total of $4.21 when you include the referral fee. I had Amazon remeasure a few months ago, but it still seems pretty high, especially when I’m doing all the work and having a supplier prep for me. Is this the normal rate? I feel like something is wrong.