I went through all the armor options in Low Tech and made a spreadsheet so I can min max armor design.
This included calculating the ultimate breastplate you can make with just TL4 tools.
Heavy plate torso with fluting, duplex hardening and masterful tailoring gets you DR 10 and 16 lb. for a mere $168,000.
Taking that corslet to the enchanter will set you back another $139,450 and up the DR to 15 and drop the weight to 8 lb.
$307,450 out the door...
That's a purely utilitarian piece, decorations would be another $36,000 for a +3 reaction roll.
$343,450 for the torso. That's not even half a full suit...
Arms will come to $143,085; DR 15, 5.2 lb.
Gauntlets are $23,095; DR 12, 0.5 lb.
Legs are $286,170; DR 15, 8 lb.
Sabatons are $20,767.50; Dr 12, 0.5 lb.
We're needing a helmet when we're wearing $816,567.50 worth of gorgeous plate weighing just 22.2 lb. In a normal or higher mana zone...
A fluted, duplex, master fitted heavy plate full helm, decorated and enchanted like the rest is $68,590; DR 15, 6.4 lb.
$885,157.50, 28.6 lb. on the kingdom's dime. The king had better watch his weight, it's THAT fitted!