You guys would love to pick holes in my sheep enterprise costings, that's for sureTo be fair to Boss, the OP asked for numbers required to pay an income of £17k, so I'm presuming that would be the wage/labour rate. So that's around 475 ewes on Boss's figures.
However I do agree with you that it's very light on fixed costs. When running through costings with my daughter for her enterprises it often seems pleasantly profitable, then I remember she has few if any fixed costs, just borrowing required equipment/ shed space off of Dad.
And it's quite easy to pluck round figures from the air to support your argument. (Even when doing costings for yourself). However actual figures spent often tend to creep well above a theoretical budget and the profit drops accordingly.
But as you say, well done to Boss for putting figures down. It's a thankless operation on here cos someone will always be along to shoot them down.
Similar to @Bossfarmer's, just without all the costs, (although my land cost is almost double his notional rent figure)