Most of the time, yes, finding a loose MVS cart versus a complete KIT is much cheaper and way easier. But when it comes to the final 3rd party releases; such as Nightmare in the Dark, Rage of the Dragons, Matrimelee, and Pochi n Nya this logic simply does not apply. Both options are prohibitively expensive and exponentially more time consuming.
They simply just didn’t manufacture very many of them. They had very small production runs and more of them sold to collectors and gamers then to operators; whereby leaving most of them complete and in good condition.
Lastly, of the 4 titles I listed, Matrimelee is not the rare-ist, but, it is the most scarce. What I mean is, Nightmare and Pochi are relatively cheap and easy to assemble bootlegs of present day, and Rage of the Dragons was heavily bootlegged back in the day. So buyers have the additional option of boots which subsequently helps keep the price point manageable on the authentic carts. But Matrimelee was either never bootlegged or done so in very low quantities. (I don’t even recall ever seeing one) So yeah, this is a spendy cart.