I just pulled these off the Miata when I installed the Koni/GC setup. The shocks have maybe 25-30kmi on them, though they're probably ~5-years old. I bought the springs used, so no idea how old they are. The OE tophats are included as pictured.
When I first installed them, the threads on one of the front shocks got malled a bit, so I just double-nutted it and it seems ok.
$150 + shipping, or delivery within a reasonable distance of 60963.