For just 1 spell and 10 minutes a day, in a few years a 7th level wizard could become rich beyond imagining.
Well maybe, but this requires a few things.
1. There has to be expensive armour in the setting - fine, this is the default.
2. The PC must have the proficiency to make that expensive armour naturally.
3. They must have easy access to all the materials necessary.
By default I would probably limit the results of Fabrication with tool proficiency to the default 5e rules for item crating, ie you can produce 25gp/day of stuff - make it 25gp per casting with 12.5gp of raw materials. But sure if the PC is built as a master armoursmith (eg they're a Forgepriest Cleric)
AND they they are a Wizard 7+ then they are going to be able to make Plate armour.
They'll get rich.
All the soldiers will wear plate armour.
The value/cost of plate armour will drop dramatically.
After a shortish time the setting will resemble Europe ca 1500, with 'foundry plate' indeed ubiquitous and pretty cheap. I'd probably set the cost of plate to 60gp, since that happens to be the cost in Classic D&D, or 50gp I think it is in 4e. I doubt the raw materials will cost much less than that.
At this point the Wizard-7 armourer probably has the wealth of a Tier 3 character, and the local city/dukedom has a lot of very well armoured* soldiers. But it's not Connecticut Yankee in King Arthur's Court. The setting is not broken.
*Hm, I think this explains how all those hobgoblin leaders & orogs in the MM wear plate armour... a BBEG wiz-7 is Fabricating it!
Re 'very rich', the DMG suggests that skilled mundane crafters are making net 2.5gp/day after materials costs. Eg you can make a healing potion in 10 days for 25gp and (hopefully) sell it for 50gp. I can see the Fabricating wizard making ten times that much (eg 5 times per casting) in line with the rules for magic item crafting. So they make 750 gp/month, when a wealthy lifestyle is only 200gp. They are certainly very rich. But the King is likely pulling in a lot more.