Maybe not variables, that won't really help except to give random names. 
It is clear they are coefficients of some sort, what isn't clear is where the numbers come from.

A reference to that would be more helpful than assigning arbitrary (but still meaningless) names to the numbers.

By my count, if we're using compressed public keys, we can actually afford to do the equivalent of:

```
bytes = (nInputs * 149) + (nOutputs * 34) + 10
Math.ceil(bytes / 1024) * feePerKb
```