Honestly I think writs are the most important reason to level crafting. You can get other people to craft stuff for you, but free mats and gold? Only you can earn that!
I’ve tracked all my max level writs for the last month and a half (approximately) – I do woodworking/blacksmithing/tailoring on one character (that has all traits and most of the styles learned), and alchemy, enchanting, and provisioning on two characters (of which, I have all the achievements but a rather pitiful number of purple/gold recipes learnt). (PS: Number of traits/styles completed/achievements/recipes learned influences the drop rate of master writs, although not their quality. Since master writs are a substantial part of the value of doing writs at max level, this is relevant. It does not influence other portions of the results).
The results are analyzed here.
A quick statistics lesson, if you’re not familiar with expected value calculations – expected value is the value of an event occurring, multiplied by its probability to occur. Another way to put it is, if you do writs 1000 times, and you add up all the returns and divide it by the number of writs you did, that’s your expected value for each writ.
I’ve used the probabilities gained from my data, and values based on MM values (plus a hefty dose of experience thrown in) to determine expected values for each possible reward from a writ. I then added these expected values together to create a total profit. You’re not going to make a 2k profit on provisioning writs most days – most days you will only get 30 food (two stacks of 10 food each and two stacks of 5 food each, plus the 664 gold for turning it in!) and a green recipe worth 25 gold. But the days when you get a master writ worth 10k or a psijic ambrosia fragment make the average value per writ around 2k.
Provisioning and enchanting are always the most consistent reward – no matter what you do you’re putting less than 50 g worth of mats in and getting (even at low level, 300 g quest reward, at high level, 664).
Alchemy, woodworking, tailoring, and blacksmithing are a good bit more variable. The average alchemy writ actually barely makes a profit as you put 3 expensive nirnroot in and get blue entoloma and wormwood out. But when you do get a survey, a single survey is worth around 4,500 gold, making it worth! Clothier is the most risk/reward – an average clothier writ costs 1,700 gold to do at the current insane prices for ancestor silk (driven almost entirely by writs). But I got an average of 8.8 master writ vouchers per crafting writ done – and at 1,300 per voucher I’ve made quite the profit. Your luck may vary of course – especially if you don’t know many traits or motifs. Still, at a 25% chance for a gold improvement item, a 6% chance of a survey, and a guaranteed 664 gold + an item worth around 200 gold, clothier, blacksmithing, and woodworking writs are certainly worth your time and materials.
Now, at low crafting levels the math is a little different. You can ignore master writs – you won’t get any. And your probability of gold items, psijic ambrosia fragments, and so forth, are a bit lower (survey probabilities are about the same, but are less valuable when done at low levels as well).
However, low-level writs are much cheaper to do! For alchemy, instead of it being a 72% chance of nirnroot, you have an equal chance of it asking for any classic alchemy ingredient – wormwood, bugloss, corn flower, lady’s smock… all of which are much cheaper. And refined mats at lower-than-max-level tend to run at around 5-10 gold apiece, instead of 15 to 65.
All of this is a fancy way of saying – certify in all your professions and do your writs every day! It only takes around 5 minutes – less if you have Dulgobon’s Lazy Writ Crafter (although be warned, don’t run it on April 1).
Also do your surveys (if you can, transfer them to a max rank/maxxed crafting character to do them). Those things are worth a loooot.