Okay, I have not yet tried this but it works for guns so a gel block should work for swords too. If you haven't seen demos on MythBusters or Fight Science, Ballistic Gel
can be molded into any form and a certain thickness block will accurately replicate muscle density. It has comparable density to animal meat, but none of the connective tissue, viscera, bone bits, and bloody mess. You can add other components to replicate bone structure too such as 1/2 inch bamboo.
Here's an image from Steven Morris
It's easier to just create a block though:
From a link on Google Images:
While official ordinance gelatin can be expensive the cheaper ordinary gel from grocery stores (yes, like Jell-O) works just as well. It just takes a bit of work to make just a block of this not to mention some place to store a large block. Most refrigerators aren't wide or deep enough; and you don't want to use a freezer on this gel.
The best part, the blocks can be recycled and reused
about two times. So one block the equivalent of 1 whole goza might roughly cost (my guesswork):
$5/lb x 25 lbs of Vyse gelatin +$25 shipping = $150 makes approx 30 blocks
Thus one goza-equivalent = $150/$30 = $5
but $5 / 3 uses = $1.67 per target.
I have not made one yet so that's very rough guesswork. Also I think we'd need to stack two blocks to make it the height of a standard goza (3 feet), so it'd really be $3.50 or so.
However, there's a lot more equipment and time involved than just a single soaking bucket and wrapping. They're not really expensive (a heavy duty stirring spoon, silicon spray, large 10 gallon pot, plastic tubs/molds of the right size and a fridge that fits them).
The other problem is keeping the blocks cool, and moving them. A soaked goza weighs 5 - 10 lbs, but these blocks are heavier (~10-20 lbs). Plus, if you want to reuse them, we would not want to do it in too dirty a floor like the park where it'd pick up gravel and twigs.
In the end, this is still much closer than cutting goza and because it's a smooth gel, it won't really abrade your sword at all. What really could make it harder to cut is the density and viscosity slowing down your sword stroke.