//In 2019 only two people got fined in the £750-£1,000 bracket.//
Then they must have pleaded Not Guilty, or changed their plea to guilty at a late stage. The maximum fine is £1,000 and an early guilty plea attracts a one third discount, making the maximum £667. The defendant would also pay a surcharge (usually called a "victim surcharge") of 10% of the fine (minimum £34) and (again assuming a guilty plea) £85 costs (but not in Scotland where no prosecution costs are payable). So the maximum all in cost would be £819.
A more common scenario would be an appearance by somebody on benefits. The fine in that case would be either a week's net income for long term evasion (over six months) or half that for a shorter term. A default weekly income figure of £120 is used for those on benefits so the amount payable would be either £199 (£80 + £34 + £85) or £159 (£40 + £34 + £85). The court may order a reduced sum in prosecution costs if it deems the defendant's means are insufficient but it may not levy less than the due amount for the surcharge. The court also has the option of dealing with the matter by way of a Conditional Discharge instead of a fine. In this case the costs would still be payable and the surcharge is £22. This is a common method of disposal for first time offenders.