Free Tier: 

• Restricted to subtraction functionality only
• No access to the numbers 0 or 5
• Limited to three computations per month

Copper Tier ($5/month):

• Unlocks addition functionality
• Can try the multiplication feature once
• Accuracy of calculations improves to only being off by factor of 17

Aluminum Tier ($7/month, must be paid in only $2 bills):

• The number 0 can be used after watching three-minute ad (ad displayed for each use)
• Exponent button made visible but still not useable
• Social feed: see what arithmetic your friends are executing

Fake Gold Tier (A lock of your hair): 

• Trigonometric functions made available if you follow us on social media
  • Facebook → sin
  • Twitter → cos
  • Yelp → tan
• No more electric shock when dividing

Silver Tier (One kidney and one other organ of your choice):

• The m+/m- buttons become available, but we provide no indication as to what they do
• Square root button made available if you message the kids from our high school about how successful we are now
• Machine learning: we’ll guess what computation you were planning to enter and display the answer preemptively

Gold Tier (Both kidneys and subscribe to our email newsletter):

• Private calculation mode: perform computations that you’d be embarrassed for your friends to see
• Instructions for the m+/m- buttons, though access to the buttons is revoked
• Every time you use the natural log function we’ll inject you with a progressively stronger dose of heroin

Platinum Tier (Create a RuneScape account, reach a combat level of 60 and then transfer account credentials to us):

• We’ll start computing your answers correctly