I know there is quite a bit contention on this and this is exactly the forum for this kind of topic.
I think the rules are pretty clear - but that does not mean they make sense or are the right thing to use. Firstly, you use the crafting rules and you pay a fractional cost - it's significantly cheaper. However, the rules get a little muddy because they do make use of terms like "Price, Value, Cost" and they are honestly not really well defined. I would throw out some rules text but everytime I do, no one bothers to read it.
No matter the numbers used, the following logic still applies.
BECAUSE "XP is a river" and people behind catch up faster...
THEN using XP to craft is barely or even not *AT ALL* a "balanced choice" (e.g. it's *BASICALLY* not a disadvantage, it's pretty much purely advantageous)
THIS MEANS while the rest of the party had "50,000gp in items" only 1 of your players, the crafter, had "100,000gp in items".
IN ONE LEVEL the crafter will have the same or more XP and MASSIVELY more items. Don't forget retraining and PsyRef et. al.
I cannot see this as being fair to the other players, ever.
This also interacts so incredibly well with "Psychic Reformation",(or re-training or whatever), to craft everything yourself at start and then PsyRef your crafting feats back into actual useful feats. Now you have a TON of extra gold for a *fractional amount* of XP; oh, and after a few fights you will catch up. That's absurd. You might as well let everyone start with double wealth by level and remove crafting if that's what you want - because that IS the outcome.
I find that using crafting to abuse Wealth By Level is exactly the same as using Skills to abuse Wealth By Level or using Salt Cows or anything else.