One of the more popular paper bedding options costs around $13 for a bag that expands to 3,000in³.
Paper bedding companies recommend using around 1-3 inches of paper bedding and to switch it out every 10-14 days. If you use 2 inches of bedding to cover your 2x4 cage, you'll be using around 3,024 in³ which means you'll be using the entire bag of paper bedding within those 10-14 days. With paper bedding, you'll be spending $32.50 a month.
For a 2x4 sized GuineaDad Liner, it'll cost you about $70 and will last you as long as you take good care of it.
By switching to GuineaDad Liners you can save $400 a year.