Not huge but not small an appropriately sized den rug from an old furniture store like the dump.
if you get lucky you may find one for around $40. you can check walmart too b/c they have them on clearance sometimes.
It depends on what you consider big. The most common shapes are rectangle rugs that range from 4x6 feet on the smaller side to 12x20 feet on the larger side. From what I gather, you must be looking for a rug somewhere in the range of 8x10 feet to 12x20. These go for at least an average of $15,000 - $30,000 for a high quality rug. I attached a reference link to a rug search inventory set to rugs that can be bought in the 12x20 size category.
