Isn't 98 about the time S&W started using MIM parts to keep labor and parts costs down?
It was in 1996, so you were close!
FWIW the change to MIM corresponded with the introduction of flat-faced hammers and frame-mounted firing pins on centerfire models. This change was also made to reduce cost. (Rimfire Smiths had used frame-mounted pins for many decades, although the design was slightly different.)
Actually, S&W Performance Center guns and some of the recent "Pro Series" lineup utilize traditional-style forged and hand-fitted lockwork, but this is consistent with the general gist of this thread; these guns are substantially more expensive than standard-production Smiths because production costs are higher, and are only sold in small numbers because relatively few buyers are willing to shell out the extra coin.