Sampson was signed out of community college, and he had a commitment to Oregon. The Pirates might have saved some money against the pool with him -- I haven't seen a figure yet -- but I doubt it'll be a ton. He appears to be more of a command/control type pitcher, as opposed to the projectable young pitchers the Pirates generally prefer, although his stuff is also supposed to be reasonably good. Baseball America ranked him the No. 84 overall prospect in the draft, so this is a nice addition for the Bucs.
Diaz was ranked the No. 430 prospect in the draft. He was one of N.C. State's better hitters this year as a junior. The Pirates announced him as a shortstop, but I'm not sure where he'll play at State College; the Spikes have a bunch of middle infielders who are vaguely interesting, but no one who's really locked into shortstop, second or third.