Can't really compare Kingery to Sanchez, that was an entirely different kind of whiff. He'd only played three pro seasons and zero MLB games when they gave him that deal. Sanchez is already in his fourth MLB season (albeit intermittently) and 10th pro season - he actually played his first game before Kingery did (due to being an international player of course).
This is basically the same deal Nola got last time, just more modest, for a less accomplished/expensive player. Nola gave up one FA year on the four-year term and a second on the option. Sanchez would have gone to arb for all four years but is giving up two potential FA years on the options.
Nobody doubts the value of cheaper homegrown talent! It's not like Klentak et. al didn't believe in it, they just failed at it.
And of course right now this deal is also a testament to the value of trading away your homegrown talent in the right deal. Even if they could still lose the deal. It's just one of the things you need to have a good farm for.