quick note about this sweater.. the total price is all in the yarn you pick. using commercially spun yarn is more affordable, generally, than homespun. choosing cotton or finding an affordable wool or alpaca will keep the cost down, as well.
you need about 1100 yards of bulky yarn for this sweater. bulky is pricey, relative to other weights of yarn, due to the extra fiber in it. its also sometimes harder to find; many spinners don't want to use a good amount of their fiber for a yarn that may or may not sell due to the extra cost to consumers.
check out & compare your options at stores like this one. keeping a ball or skein of yarn (usually 100 yds in length) at or under $10/ea will keep your fiber cost for the sweater/belt to about $110. there are many that cost less than this, too. its very possible to buy this sweater, fiber & all, for as low as $100, or as high as $400, depending on the yarn you pick.