As said above, an owner-operated business will command a lot lower value, certainly goodwill in the 1-4 multiple of net profit territory plus stock and F&F at current market value.
You have to remove the owner and their family "notional" wages - so, say a corner shop, if it makes £75k profit by the owner, spouse and their kids running it for pocket money, in reality, if a proper paid manager and staff were used instead, there'd be virtually no profit, so it would be effectively worthless - maybe 1 times profit if you're lucky and can find someone who just wants to buy a job for himself and family.
If, however, that £75k profit was achieved after paying proper staff and management, and the owner and their family didn't take an active part, then it's more likely to sell for 3 times profits or higher. An even higher premium may be available if it was to be bought by a chain or someone who already had a few shops and wanted to add a successful one to his portfolio, to gain economies of scale etc.
At the end of the day, a "one man" business is always going to be very high risk for a buyer. The price will reflect that high risk. Most won't have robust systems, too much will be in their head, the "personal" relationship between the owner and his suppliers and customers will be hard to replicate.
Profit multiples of 6,8,10+ times profits are the stuff of economics textbooks and the stock market.
I agree with another earlier comment about the asking price being based on what the seller needs to sell it for rather than what it's worth. A lot of the time, they want to get back the price they paid for it a couple of years earlier when reality sets in and they realise they overpaid, or they need enough to pay off their loans and overdrafts. Very, very, rarely is it based on any meaningful formula - more like a guess.
And yes, the real prices achieved are often far lower than the asking price. A case I acted for on behalf of the buyer last year, the selling price was £110k and the agreed price was £50k being £25k upfront on purchase and the remaining £25k being repaid on loan at £5k per year for five years, interest free! We've just done the first years' accounts which have showed a £40k profit, so the price was effectively 1.25 net profits.