I do not think that you can craft them cheap, as to craft it you need to clear mythic raids (and I am not sure, possibly high end M+ dungeons) in order to get the upgrade material that bumps up the ilvl to that point.
Most also require a Spark, which get two every month, so by the time you get to equip yourself with a full set the season will already be over.
That said, some crafted items are limited on how many you can wear of them at one time.
If youve got the upgrade material necessary to add the item level? Yes. However those come from higher end content (Mythic bosses and dungeons 16 or higher)
You get one spark every 2 weeks.
Crafted gear is half way between bad luck protection and catch-up gear, it’s not an alternate gearing path of its own besides maybe getting to 405 ilvl.