1.58 x .9 + 3/12 x .9 = ~1.6

You need to apply overpay

Other than that it looks good.

Rounding is ok. You may want to consider 1.8, rather than 1.81.

At least, that's what I would say if the sale was in pure. Since it wasn't, you need to take all non-pure items and multiply their value by 0.9. In this case, it turns out to be around 1.6 buds.

Also, have there been any other recent sales? If there are you might want to include them.

Other than that though, it looks fine.

As indicated, overpay will need to be applied, putting the sale at ~1.6

Have a look at our guidelines: http://forums.backpack.tf/index.php?/topic/6033-new-unusual-price-suggestion-guide-the-cheat-sheet/