The short explanation is that used/resealed stuff tends to be way cheaper than buying new here in Japan (loose stuff even more so), so for mass-retail stuff I usually pass on it until I can find it second-hand. Masterpiece TFs and most 3PP stuff tends to go the opposite way and get more expensive over time, though you do find the occasional used 3PP bargain.
In this case, all the TT Hoist-&-Trailbreaker sets I can find right now are a bit more pricey than I'd like.I'm pretty sure one of them will show up used (and therefore cheaper) at Mandarake or Jungle sooner or later, or even on clearance price at my closest Toys R Us, but by then the upgrade kits will probably be gone. I checked the online prices for the kits and it worked out more or less the same after postage, so it seemed worth getting it now and waiting on a cheaper base figure set than the other way around.
The end result should be the same, but a little easier on my wallet.![]()