The crafting system will take what is provided in DMG and XTGE, and modify some rules to suit the setting and campaign. 
For instance, in Eberron, all magic items of rarity common and uncommon are able to be acquired as if they were "common". This means that items of both rarity are widely available for purchase at relatively "reasonable" prices. Note that just because the availability of these items are commonplace, it does not mean you will be able to buy every such magic item everywhere you go. Magic items will be placed where they fit within the nation you are in, and the choices I wish to provide for your character customisation. Every magic item within canon sources will not be available. For example, Thrane would have a greater focus on divine magic items whereas Karrnath would be more tailored towards magic weapons and armour. Location will factor into availability.  
What this means for crafting is that common and uncommon magic items and potions are able to be crafted with relative ease, provided you meet the pre-requisites detailed below. In addition, for artisan "professions", general character proficiency bonuses will be supplemented by specialised crafter proficiency bonuses, detailed later. 
Common All common magic items can be crafted if you meet the tool proficiency, can cover the gold cost of materials and spend the time required for crafting.   
Uncommon In addition to above, uncommon magic items require formulas. These formulas can be easily purchased throughout the world. Any ingredients required for these items are also easily sourced from markets and dealers in the world. 
Rare & above Magic items of rare and above are scarce. Formulas for these items are either lost, or heavily guarded secrets. Only true masters of their craft are able to craft such items and finding these individuals is difficult. Ingredients required for these items are unique and serve as quests in their own right. 
Magic Item Crafting Time & Cost
Common 1 wk 50gp
Uncommon 2 wks 200gp
Rare 10 wks 2,000gp
Very Rare 25 wks 20,000gp
Legendary 50 wks 100,000gp
*Halved for crafting consumable items like potions.
Spell Scroll Scribing Time & Cost
cantrip 1 day 15gp
1st 1 day 25gp
2nd 3 days 250gp
3rd 1 wk 500gp
4th 2 wks 2,500gp
5th 4 wks 5,000gp
6th 8 wks 15,000gp
7th 16 wks 25,000gp
8th 32 wks 50,000gp
9th 48 wks 250,000gp
Copying a Spell into a Spellbook
Can only copy a spell into your spellbook if it is one you can prepare and cast. The costs associated represent the fine papers and inks required, as well as the time to decipher and transcribe it in your own notation.
Process requires: 2 x (spell lv) hours 50 x (spell lv) gp
Crafter Skill Not all crafters are created equal. While a village blacksmith may be good at fixing scythes and making nails, if you hand them a dragon scale, the best you'll get back is a ruined dragon scale and an apologetic look. Under the base rules, anyone can craft anything as long as they meet the base proficiency requirements and minimum level. Under this new rule, crafters are differentiated based on their skill level. A crafter may craft any item whose rarity is equal to or below their skill level. When crafting an item, the individual adds their proficiency bonus and their skill bonus to the roll. 
Note that different items may require multiple proficiencies and skills. For instance, to craft armour, one would need to be proficient in smith's tools. To enhance the armour with magical mechanical wings, one would need to be considered an "artificer", have proficiencies with both the smiths and tinkers tools and be at the required skill level in each tool. As a result of this new feature, a character's artisan skill level may surpass the proficiency of their character level. Thus, legendary items need not be crafted by lv17 "adventurers", but by extremely skilled practioners in their profession. 
Hence, skill proficiency in artisan pursuits are no longer purely derived from a character's level. It is now treated as a separate downtime activity that a character may pursue, through the acquisition of rare books, the seeking of forgotten masters, and general practice and experimentation. 
Skill Level Item Rarity Skill Bonus Description
Novice common (+)0 Usually an apprentice, assistant, or self-taught practitioner. Knows how to use the tools properly but has little skill with more difficult materials and no ability to make new ideas.
Journeyman uncommon (+)1 A craftsmen that serves their village or works in a specific role within their profession. Knows a few things very well, but most likely would not be able to understand the complexities of more exotic materials.
Artisan rare (+)2 The highest level of skill that most ordinary people could hope to attain. Capable of establishing a good trade in a city or in service of a noble. Experienced in almost all aspects of their profession and can work with some confidence on rarer materials.
Master very rare (+)3 While hard work and dedication is always valuable, only a few people possess the inherent talent to push the limits of their craft farther than ordinary people. These talented individuals can be considered masters of their art; capable of not just reproduction, but innovation.
Grand Master legendary (+)4 An absolute master of their art. Most likely was either an adventurer in their past, or learned their trade from a supernatural force, as this would be the only way for them to become accustomed to the legendary materials that they work with. Capable of crafting any item that falls under their profession.