
The most direct way to essentially pay nothing for Magic cards is to find preconstructed decks with individual cards that add up to more than the suggested retail price of the deck. The most obvious example in recent memory of this is the Magic Origins Clash Pack. Touted as perhaps one of the best values that Wizards has ever produced on a mass-market product, it contains 4 cards that see play in the growing (and eternal) Modern format. They are Windswept Heath (the popular “fetch” land), Collected Company (the lynch-pin of a popular and competitive deck), Dromoka’s Command (a very useful sideboard card), and Siege Rhino (once a staple creature in Standard with obscure play in Modern).
Back at this deck's release, if you combined the retail price of those 4 cards, you get a number close to $25, or the price you can commonly find the deck for online and at local stores. Were you to list them on eBay or TCGPlayer, even after fees and shipping, you’d pretty much have a free deck, give or take a few dollars.
So, back in say January 2016, what would you be left with?

These prices mentioned are the lowest retail price minus 15% for fees and shipping, as of late-January 2016.
Windswept Heath - $10.25
Collected Company - $7.25
Dromoka’s Command - $2.00
Siege Rhino - $1.50
Total - $23.50
At the time when I first wrote this article, I said that the prices would likely creep up over time. How has that turned out?
Prices as of July 2019:
Windswept Heath - $12.75
Collected Company - $12.75
Dromoka's Command ($1.00) and Siege Rhino ($0.50) aren't worth even selling as singles any longer.
Total: $25.50
However, the deck in July 2019 costs at least $36 retail. It's no longer exactly free. Still, let's see what's happened with the rest of the deck.

Avatar of the Resolute $2
Anafenza, Kin-Tree Spirit $0.75
Sandsteppe Citadel (foil promo) $0.75
Valorous Stance (foil promo) $0.50
Honored Hierarch (foil promo) $0.25
Abzan Ascendancy $0.25
And a bunch of bulk rares, uncommons, and commons
Roughly you’re left with $5 of leftovers. Back in the day, they cost you less than $3. Now, had you bought the deck at $25 (or somehow still acquire it for that price), they are, in fact, completely free. Plus, these leftovers are far from being the worst cards.
Avatar of the Resolute is played in Mono-Green Modern decks. Valorous Stance is a pretty useful card, although it really has only seen play in Standard. Sandsteppe Citadel is mostly used in Abzan (White/Black/Green) Commander decks, but this foil is definitely sought after. Anafenza, Kin-Tree Spirit is a major combo piece in Modern Collected Company decks, and the only reason her price is so low is her supply is so high. Abzan Ascendancy is a bulk rare but one that some people want.
Unsurprisingly, Windswept Heath has regained value over time as soon as new copies aren’t hitting the market. Collected Company once again reached $15 as it once did. Unfortunately, Dromoka’s Command dropped to $1 and Siege Rhino has mostly faded from sight. You would think Anafenza, Kin Tree Spirit isn’t going to remain $0.50 forever. But, it hasn't increased yet.
Sure, this deck was a much better quick-flip when it first released than it is three years on. Of course, if you held the deck all this time, you are, in fact, still ahead. But this example goes to show that it is possible to play Magic for essentially nothing. All you have to do is identify the cards that will retain their value and perhaps even gain in price in the future. While it may seem a bit boring on the surface, having guaranteed value in your collection means that if you ever need to sell your cards, you know you have put your money in the right place.
There are other decks out there with similar returns on investment. We’ll be covering them more in the future as we continue this “How to Get (Mostly) Free Magic Cards” series.