I've shipped 2-3 through UPS for way less than $400. If I recall, it usually comes in around $80 or so. You'd have to box it, and it's difficult to do being sure that the part can not move inside the box. That requires 20-25 pounds of tightly packed packing. Remember, if it can move in the box, it can find it's way out of the box. Also, make sure to completely drain it, and use 2 large garbage (on from each end/overlapping) to ensure nothing leftover can leak out. Fluid will compromise your box in short order.
Another option is to build it a wooden crate out of 2x4 base, and 1x4 sides. Run two 2x4's side to side to sit the tranny on with the bellhousing hanging just over the edge of the front one, and a good solid place near the back. Once you get it in a steady place, place two 1x4's on top of the tranny. One will go right behind the bolt holes in the bellhousing. The other, again will go in the best place you can find near the back, maybe over the shift hole. Those boards will protect it if the pallet flips. Drill 2 hole in both end pieces, and run a piece of rope so that they can use it as handles. This thing is going to push every bit of 150 pounds, and handles will assure it stays right side up. With no handles, they will beat the shit out of it by rolling it.
