I have two 14.5" SBRs
Prior to the stamps, I had two colt SOCOM barrels with pinned phantoms. I eventually wanted to swap rails and what not. Using ADCO to complete the work, it's $30 plus S/H to pin the FH in the first place, $40 plus S/H to send it back to be removed (OR risk damaging your muzzle and DIY), and $30 plus S/H to send it back after the work is done and have it pinned again. Assume $10 round trip shipping (probably more) each time, and you're already at $130. If you pay ADCO, to tear down and rebuild the upper you save $10 S/H but it costs another $50. That's $170. A tax stamp costs $200.
If I want to go shorter, I can.
If I want to swap muzzle devices, I can.
If I want to tear down the upper completely and rebuild it, I can.
If I want to put a 16" OAL upper on it and transport it like any other title I firearm, I can do that too.