It isn't actually the CAA's power to fine for this, just to prosecute. Any penalty will rest with the sentencing
court, in accordance with sentencing guidelines. The guidelines as to the amount of fine imposed require the court to take into account the "relevant weekly income", amongst other things, of the offender. A typical maximum would be around 150% of weekly income; so a premier league footballer could expect to pay more in cash terms than a school teacher.
MB
(This is not legal advice - consult a lawyer if this affects you)
cf Sentencing Guidelines Council