Pretty close Val. To be accurate, one needs to use a spreadsheet to take into account the positive impact of you being charged a lower total tax since you would be buying them at a lower total cost, but then offsetting this savings with the fact you only get 15% commission at your price vs. at the normal buyer's price.
The total you came up with of $202.89 includes a 9.25% (OMG!) sales tax. Divide this by 75 cards and she really is paying $2.705/card effectively. It took me about an hour, because I can be THICK at times, but I was able to generate a table of equivalents for you. The first column is the equivalent of a reduction from the normal retail card price, if that is the way you want to present it to her. Like in your example, an equivalent reduction to $2.19 really would cost $2.62 with tax and shipping. In this case, you'd charge her $196.50. You'd make $47.65, well above the normal commission of $34.35 on 75 cards.
The colored column is your profit if you bought 75 cards and needed to discount them further in order to close the deal with her. You can negotiate to as low as $2.05/card equivalent before you end up making less profit than if she just went and bought the cards directly. By the way this comes at an 11% "discount."
The last line represents a case where you make nothing, which matches the $1.61/card (or so) artist price with commission removed. <Some rounding effects in the spreadsheet>
There is a lesson here for everyone. There is a wide profit range possible doing what Val is doing here. You can still make $ as long as you resell above your total cost. In her case, her break-even cost is $1.98/card at qty 75, well below the $2.705/card a normal customer in her area would effectively pay/card. (That's a 26.6% discount window to play with)
Make sense? Seems you have a good opportunity there Val! GOOD LUCK!