That depends. Do you need the concession because you have hit a wall in your grind or do you need a home for extra companions?
I used it as storage for companions for several days before it seemed worthwhile adding a workshop to continue my woodwork grind (unless I'm missing something there is no way to grind past 22 woodcutting on Hawkoria materials/trees alone). It let me grind up a full contingent of foresters to have 24/7 log or hunting income, start building a combat/dungeon team and keep other handy companions (guide, page) for future use.
The base cost is more than worth it for that.
I get blades in Turnbull woodcamp - fir logs + firewood. Granted, I did have to buy the later on the market few times as you need 20 of it for a single blade.
Your method does seem more profitable though, if we dismiss the starting investment in hunting. Will think about doing that, thanks.
I'm mostly assuming this as a given cost. Fauna is damn near required to learn as it gives you taming, close to mandatory for dungeoneering. Many (most?) worthwhile combat companions are beasts, and it lets you split your companion capacity between your authority and dominance and have more high-value companions than sticking to either of them. Hunting is easy to get on the side, nicely profitable, and the fish only requires 6. A baseline Forester will always beat 6 hunting, so can be left to fish immediately after recruitment.
The fir and firewood trade is more time consuming to gather deliberately (fastest source of 20 firewood averages to 51:04) and actually higher base value goods (20c vs 25c, so not vast difference) which also have actual uses elsewhere. That said, if you have the surplus and absolutely no blades it's not the worst thing you can do with them, but I wouldn't make the trade in bulk.