Comment by agwa

Namecheap's current .com renewal price of $14.58 is broken down as:

  $0.18 ICANN fee
  $8.97 Verisign's current registry fee
  $5.43 Namecheap's markup

Namecheap's new .com renewal price of $15.88 will be broken down as:

  $0.18 ICANN fee (no change)
  $9.59 Verisign's new registry fee (7% increase)
  $6.11 Namecheap's new markup (13% increase)

So the price increase is not entirely "out of [Namecheap's] control". They are also increasing their markup.

Edit: fixed error in Namecheap's markup - thanks everyone for pointing that out!