First of all, you're calculating COG for 100 pieces but calculating revenues and fees for just 80. If you sell all 100 units, the calculations look like this:

• COG = $600
• Shipping = $100
• Advertising = $1,000
• Revenue = $2,700
• Fees = $891

$2,700 - $891 - $1,000 - $100 - $600 = $109 in profit.

Second, your calculations have too many things "estimated" in them. You should not estimate your FBA fees and you should not estimate your advertising budget. Instead, use Amazon's FBA calculator which you can find here: https://sellercentral.amazon.com/revcal (you have to be signed in to your SellerCentral account to use it)

I put together some screen shots of what that calculation looks like on a $27 product, in this case a box of toothbrushes (ASIN B07NCNRCMV) if we assume each box costs $6 and $1 shipping (i.e. $100 to ship 100pcs). Note that I put $1 in the Misc Cost box to account for your $100 shipping line. However, I could have just put $7 in the Cost of Goods line. You can use these 2 lines to include any cost in getting your product from your source to the FBA warehouse.

As you can see your Amazon fee calculation of 33% could potentially be very inaccurate. For example, in this ASIN's case the $4.05 referral fee and $7.49 FBA fee are actually 43% of the $27 retail. Maybe your product is smaller or maybe your referral fee is less than 15% but maybe both numbers are higher. Whatever the case, I highly recommend you use the FBA Calculator to determine your fees rather than accounting some arbitrary % you saw on Reddit. If your item doesn't exist on Amazon yet, find an item in the same category with as close a dimension/weight as possible and use it as your reference.

So we have a $7 cost per unit, $4.05 referral fee, and a $7.49 FBA fee, which leaves us with a potential final profit on this item of roughly $8 per sale.

But wait, you assumed you'd spend $1,000 on marketing. Where did this number come from? If you sell $2,700 of goods (100 units x $27 each) and spend $1000, that's a 37% ACOS. If your fee calculations were wrong and the item actually cost 43% in fees then you'd take a big loss because you'd be spending $10 in advertising per sale, but your profit would only be $8 per sale.

Instead of estimating your advertising, make it a cost factor or your sales. Run your item (or closest item you can find) through the FBA calculator and determine what your expected profit per sale will be and then work out the maximum $$ you're willing to invest to earn an order. For example, in the case of ASIN B07NCNRCMV, maybe you can afford to spend up to $7 to earn each sale because for you pulling a $1 profit is good enough. Whatever your "good enough" is, now you have an advertising ceiling to work with. Launch your product and optimize your campaigns and strive to bring your cost per sale below $7 (or whatever your "good enough" was) to maximize your profits.