First of all, I would like to point out that the total cost of each deck after you've ordered it will come to around $18.50 ($10 for the digital files, $8.50 for the physical deck). You're not really getting charged twice as much as the single payment is split into two payments.
But we know that it's a little confusing, but there are several reasons we've decided to use At Cost Codes to cover the distribution of decks, books, and posters.
First, backers get a chance to check out the PDFs and try the print-and-play cards, then decide whether they'd like to spend the extra to order actual physical copies.
Second, international shipping costs may be somewhat pricey, especially if you're ordering only one deck. Doing things this way allows backers to group all of their decks with other purchases they may make on Drivethrurpg to save on shipping. We can also make the decks available as we finish them, which will let backers grab the first decks finished and toss them in with another order they were making on Drivethrurpg, then grab the rest of the decks later when they come out.
Third, we live in Asia and fullfilling the orders ourselves would be immensely expensive. Any benefit of ordering in bulk would be offset by the incredibly high shipping costs.
Fourth, by not collecting that money, we are also not liable for paying the Kickstarter fees, transaction fees, and taxes on it. I (Ben) live in Japan where the money will be processed and will be liable to pay sales tax on all of the money raised by Kickstarter. By having Drivethrucards.com collect that money, we avoid paying these fees and can keep the price of backing the Kickstarter lower.
Fifth, and most importantly, we're just a two person team and this fulfillment method significantly lowers our burden (we don't have to process all these orders) and allows us to focus on making cards as quickly as possible!