I would disagree.
Bogaerts had a down year overall but he absolutely crushed it in the first two months and in September, so he's shown the ability to be an impact bat. His struggles in the MLB in 2014 should translate to a very good second season, as he was able to make the adjustments he needed to make toward the end of the season.
Betts, we agree on. He posted a 2.1 bWAR/1.8 fWAR in about 1/3 of a season. He basically played like a 6 win player last year (insane).
Vazquez isn't going to be an all star, at least not yet, but he did throw out 52% of the runners (which is insane), and put up a .308 OBP. Nobody needs him to be an all star caliber hitter. If he can hit you .250/.320/.350 (he hit .240/.308 last year with a .283 BABIP, so a bump to .250/.320 is very reasonable), and provide the defense he provides, he's an excellent player (last year he posted a 1.1 bWAR, 0.7 fWAR over 55 games. That would translate to around a 3.0 bWAR and a 2.0 fWAR over 150).
Buch and Kelley - Nobody is asking them to be aces. They can absolutely provide serviceable innings at an extremely low cost. This is what allows you to go out and spend $40mm on two top-of-the-rotation pitchers.
Webster is a crap shoot. He played well in September, but who knows with him. The #5 slot could be a constant rotation between rookies next year (Webster, Johnson, Owens, Rodriguez). Either way, you're paying them league min and getting league average, maybe a tick below league average production.
The point is, you've filled out your roster with a lot of extremely cheap talent that has very high upside (see Buch 2013, Kelley 2013, Betts 2014, Bogearts upside is immense). And that is how you are able to afford guys like Lester and Sandoval on the FA market, and it doesn't cripple your team financially.
This team has $42mm locked up for 2016. $42mm. That's it. They have done an excellent job in keeping deals short term so that, if a deal doesn't pan out, it's not 8 years of smothering dollars. Now, they'll have to get away from that plan with Pablo and Lester (unless they go Headley on a 2-3 year deal), but that's just 1-2 players.