un-gold = 100
re-gold = 200

i bought this item costing = 150

So,

un-gold = 0
re-gold = 150

Now, dota_item_purchased is called,

Current un-gold = 0
Current re-gold = 150

item cost = 150
gold left = 150

if 150>=0 then // true
	modify gold ( Current un-gold - gold left) // 0 - 150 = -150
	// erraneous?