Is this something I should worry about? Or is this just Spectrum scaring us into buying it directly from them at a premium?
Heres option #3: It could be that the headshop scored such a helluva deal in buying it by the bulk, that they are not hurting their profit margin by selling at $19.99.

If you are concerned that the QF batch from the headshop may be bogus, you can always run your own validity test on the batch to see that the creatinine, S/G, pH, etc; are all within acceptable limits. These test kits are inexpensive and can be found by doing a Google search for "drug adulteration test kits"