Casty when we already had Schwarber was dubious as well, but Casty at least could play RF when Harper had to go to 1B. Signing Casty most likely also cost us Hoskins unfortunately.
Merrifield for 4+ months at 8M not a good value either, but the short duration much more manageable than multiple year overpays for Casty and Walker.
Turner & Harper are likely to be bad values near the end of their deals as may Wheeler & Nola, but that is the cost of business for players of their high caliber. The issue to avoid is paying lower quality players top money.