Snap On is smarter than that. The warranty cost is built into the original price. They can sell tools at 50% to tech students and still make a profit, so for those of us paying full price, we're practically paying for them to make a second tool already.
Do you really think they are making money at a 50% discount? SNA's 2015 numbers show a
gross profit margin of almost 50% (including their lucrative financing operations), and only a 14%
net margin for the business. The numbers for 2014 were similar. The numbers for 2013 and 2012 were worse.
I think it's much more likely that promotional discounts to tech school students are just that: promotional! They're a loss leader, intended to get kids "hooked" on Snap-On tools and Snap-On culture. Those discounted hardline tools will be paid for many times over when the same guy is financing a scantool at 25% APR a few years down the road.
The loss leader is quite a common business practice, so much so that I can name quite a few even if I restrict myself to automobiles. There have been widely-reported stories of compact cars being sold at a loss in order to introduce young buyers to the brand (sound familiar?). Some dealerships will order 1 base-model car and advertise it below invoice, but you'll find when you arrive that the unit in question has been sold and only its better-optioned brethren remain on the lot. Oil changes are offered for $10 in hopes of an upsell found during the multi-point inspection. Alignments are under-billed at $49.95 because they usually uncover suspension issues.
Let's all dismiss this notion that tools can be made in America, to exacting specifications, with a lifetime warranty, on the cheap.