Spanish Cedar Lumber

Question about guitar making?

I plan to make a classical guitar. I was going to use Spanish cedar for the neck because I want to make a flamenco. I priced Spanish cedar on a website that caters to guitar makers and it was about 5 times more expensive for the same dimensions than Spanish cedar from a general lumber site. Does it make a difference if I buy the wood from a luthier store vs a lumber store as long as the dimensions are correct?

It sure makes a lot of difference.
The quality of the wood you get from a lumberyard is far lower and inconsistent.
While in theory you might get a piece that’s suitable, in practice it rarely if ever works out that way.

More knots, bad grain, improperly weathered and cured, etc.etc.
Good enough for doorframes and shoring, not good enough as tonewood for musical instruments.