You don't have your platform listed, @Baranthus ... so the top and bottom motifs are going to be slightly different depending on the EU platform you're on.

That said, the cheapest ones are the original game release purple motifs that can be found in whole books:

Barbaric
Primal
Ancient Elf
Daedric

These four (4) are a very inexpensive way to improve your chances on master writ drops quickly.

The lowest cost motif that is in individual chapters is certainly the often-found Mercenary which drops in vet dungeons.

Celestial (found in Trials) is also cheap and plentiful at the guild stores. It also makes some nice-looking gear including the staff.

Finally, if you can find all the chapters, the Holiday event motifs (Hollowjack, Skinchanger) are still cheaper than most ... because they drop like candy in the limited window that the event is held. ZOS has confirmed the Hallowjack event is returning. Therefore, prepare yourself for another flood of these at the end of next month.

The motifs that tend to be pricey are the ones that you can't find in the open world.

The drop rate on Buoyant Armiger is embarrassingly low and also behind a paywall (found in Vvardenfell chests). So, you might as well just consider it not found in the open world. We're still trying to figure out the ZOS logic on this one ... it's not really one of their better-looking motif styles so why make it rare to find?? The idea must have been born in a haze-filled conference room, off-site, and late at night. Or, a shorter answer is "cause ZOS".

Some motifs are bought with a different currency rather than in-game gold ... making them specific to that playstyle and rare.

Akaviri and Militant Ordinator can only be bought with high amounts Alliance Points (AP). So, unless you are in Cyrodiil 24-7, these aren't easy to acquire. The AP to gold conversion is very different based on the platform and server you're on. It can be as low as a 3 to 1 AP to gold conversion ... which doesn't favor the buyer. In addition, these chapters are difficult to find in the guild stores at all.

Another motif, Ebony, can only be bought with writ vouchers from Rolis Hlaalu the master writ vendor ("Mastercraft Mediator" is his official title). Because the motif is available to master crafters only, the conversion price to gold is high. The light armor version of this motif, along with the weapons, are quite nice too.

Other motifs, even though open world, are expensive because they are associated with a long grind or difficult content. In the case of Silken Ring and Mazzatun it is both difficult content and a long grind. The Shadows of the Hist vet dungeons are a challenge ... players will often leave your dungeon-finder PUG group even on normal. After that, you might complete it on vet, and still have a chance of not getting a motif chapter drop.

The dailies in Craglorn are really long and sometimes require 2 or more players to group up and complete. Hence, chapters of the Yokudan motif aren't often found for purchase. Ever tried to solo Spellscar "Critical Mass" quest? Yeah, that one isn't fun unless you have a group together to help. I'm still trying to find a Yokudan chest motif on NA PC.

Finally, newer motifs from the most recent patches will always hold some value. On NA PC, the Morrowind-specific books of Redoran, Hlaalu, and Telvanni are still holding at 15k-20k per chapter. Best advice is to avoid these motifs for now and find other chapters to focus on until the price goes down.

Hope you find this info useful. Good luck!

As a tip from a motif collector, a strategy I use is finding the 4-5 motif farms I really enjoy playing, then I collect those to sell and use the cash to buy ones I need. I really like running the dark brotherhood and thieves guild dailies...I can do bothnin about 20 minutes on my NB. So each reward dark bro or thieves guild motif is sold for ~20k and I but the ones I don't want to grind for.

Most people don't think to do this...but there are some spends motifs that can be obtained 10x faster than others at the same price level.

Also, always watch for game events. Motifs are commonly an event reward. I make 4 million during the birthday motif bonanza.