Jesus that sounds borderline impossible at £1k per week which is about 4 x 1 hour punts per week every week unless he was splashing the cash at the high end £500 per market.
Smiths is/was a often staunch, bordering repetitive, proponent of
'There's no correlation between price and quality-of-service' in the debate that periodically rears its head here. I just had a quick shufty through his recent reviews, and his most common experience, at least those reviewed, seems to be a 1/2 hr slot from £60-80 - so, yes, if that was typical, it would take some going to reach £50k pa. But he was prolific, often talked about his 'regulars', and given the restraints on posting repeat reviews, there's every reason to expect his 285 or so reviews represented <10% of his total punting.
It's easy enough to see how it can happen if money is no problem and you have a taste for it.