Okay so a portable hole with a 10 ft radius (20ft wide) by 15 ft deep would be 4714 ft cubed. Multiply that by 700 gp and then .25 (legendary artisan) to get 2474850 for the adjusted base price, followed by X .5 to get 1,237,425 as final crafting price and 98,994 xp.
Holy crap! Is my math right...