It's only of use as a thought provoking article ... the assumptions made are so fundamentally flawed and there are so many omissions it's a waste of space as anything approaching a financial model.
The reality is that anyone with four hives would be very lucky to break even as an average of the first few years. Even if you accept that the 'profit' suggested in the article is achievable (which is doubtful) if you then further extrapolate and say that (for arguments sake) you spend 4 hours a week during the season from March to October on managing and maintaing your four colonies .. that is at least 120 hours of work for a return of £550 ...Just over £4.50 an hour - and I think, even that, is optimistic.
The reality of keeping bees is that, once you have established a few colonies (probably 20 - 30), have absorbed the cost of the equipment needed, have the time to spend looking after them and are not costing in the time that you spend beekeeping then it can produce an icremental income. Once you get above that number the cost/profit curve steepens as you need to consider the costs and logistics of maintaining a larger number of colonies and whether the increase is worth the effort.
I know a few beekeepers in the bracket 20 - 50 hives and I know how much work is required .. and we've discussed the costs and profitability. As a second income and an enjoyable hobby ... it's great. As a full time business .. it's a minefield and potential money pit.
If you have several thousand pounds to invest in a beekeeping enterprise you would be better off putting the money into a managed investnment fund (Mine makes on average 10.45% a year) - even with the current massive drop in share prices my fund manager got me an 8.8% return last year - probably more reliable than risking it on keeping bees in any quantity.
https://beekeepingforum.co.uk/showthread.php?t=8543&page=2790 See JBM's post !! - And he has a full time job ...