I suppose so. But the Lisa was such an expensive, high end computer, the cost of a mechanical keyboard would've been insignificant.
Even the Mac, which was meant to be a more affordable alternative, used a mechanical keyboard!
There must've been more to it than cost. Feel, perhaps?
I'd imagine that the Lisa keyboard is significantly quieter and softer than an equivalent mechanical one, yes?
c
I'll let you know when mine is restored!
But truth be told, there are several keyboard technologies or production runs which turned out not so good regarding longevity.
I'm also restoring a TRS80-model III, uses a keyboard with the rubber domes, and also is a disaster with about a third of the keys not working at all, and lots of the others suffering from keyboard bounce (multiple strokes registerd when only hitting it once, even with the "software" filter they programmed into basic).
And a disaster to repair as every bad switch has to be desoldered and replaced (have a broken donor machine with enough working keys to get the other one complete).
Apple also had the "film" keyboards as used in the Duo series laptop's, another total disaster!
At least the restoration of the Lisa keyboard is fairly easy, with getting the protective layer sepparated from the double sided tape of each little foam pad being the most annoying part!