Guide is good at providing starting levels for some crafts but its misleading as you do NOT make money following this guide (at least 1-26)
The 800 and 1000 vendors are overshadowed by shard costs alone of 800g being generous along with 300-500 cloth you are still losing money it just "seems" you are making money because your currency goes up.
In actuality its sort of like trading your shard reserves for gil up front (at lower premiums). If you make your own shards by desynthing fish sure you will make money, but it will still be less than just selling your shards in the wards.
Btw Canvas Wedge Cap actually makes money (even AFTER shard costs) so I was surprised it wasn't on your list and it bridges your 20-26 gap you left open (its a 24 synth).
These vendor for 1984 and cost yarn + canvas + cotton which cost 800 (but i usually see them for 350 apiece, both types). Shards are 8x so with shards and cloth costs its 1500-1600, making net profit of 350-450 or so per synth (this is assuming Cotton yarn is free, which your guide seems to assume).
Basically what I'm saying is yes you may have more gil at the end when you are done with this guide, but its all from your shard reserves. If you buy shards to follow this guide you will not gain any money because shards sell at higher premiums than what you get return off these synths. If you're just looking to make money just sell your shards and save yourself some time, but if you want to level weaver its a decent guide at best.