Not to be a kill-joy, but paypal charges you 2.9% on the tax received as well (tax is charged against sale price + shipping). Also, what are your shipping supply cost? Used box vs a new box?
I track what I actually receive into paypal vs what the sale in ebay says and I couldn't figure out why it was off - sometimes by mere pennies, other times it was over a $1 and yet other times, it was dead on correct. What I discovered is Paypal takes their 2.9% off everything received (sale price, shipping, and the taxes paid on your sale). Paypal then automatically returns the taxes paid back to ebay. If you look at the detail paypal transaction you'll see it all. On a side note, I wonder if paypal is collecting another 2.9% of the tax returned to ebay for each sale. If they are, that is quite a racket.
So your sale of 73.50+14.99=88.49 * 6% tax (middle of the road example) = 5.31 taxes.
Paypal 2.9% + $.30 of total (93.8) = 2.72+.3 = $3.02
Ebay 10% of total ebay sale (88.49) = $8.85
So your sale minus fees plus shipping difference is actually: 73.50+14.99-7.60-8.85-3.02=$69.02 - 63.58 = Profit of $5.44.
Now subtract any new shipping supply cost. Of course, this estimate doesn't include gas if your taking it to the USPS or the cost of gas to buy the product or get it home, but that's just anal retentive...
If you used a Red Card to purchase it, that would add roughly $3 to your bottom line. So your buy-in would actually be around $60.58 for a Profit of $8.44.
I have a spreadsheet that does all of this for me. The tracking of the tax amount pd (and paypal percentage on that) is what I'm currently adding into my spreadsheet right now.