So many things can be pitched, but let me use for example. Let us use the Svengali deck.

I understand the ideas of the pitch, however where is the supply for this deck coming from?

Is there also a mark up happening as well?

Thanks.

Louis if you use the advanced quicksearch looking for postings with the word Svengali in the title only (so klick on title only) you will see lots of threads about sources for the Svengali deck. Keep in mind that in the last two years prices got much higher.

Louis, you can get Svengali decks from a lot of on-line resources. Keep in mind the old saying of "You get what you pay for" is very true.
Many of the decks are really cheap card stock, many are bridge size which is okay for kids but not favored by adults. The decks look like a magic trick.
I personally make my own Svengali decks using Bicycle or Aviator stock. I do all the necessary work needed to create a deck which results in a high-quality professional looking product.
Originally, I purchased my card stock from Costco but now purchase standard decks wholesale to save a bit of cost. The cards from Costco were inexpensive enough for me to still generate a modest profit.
It is a lot of work but if you are like me and particular about the product making your own is the route to take.