Arms Export Control Act of 1976 governs all defense articles and services. It has ALWAYS applied to gun manufacturers, gunsmiths, gun trainers, etc. Most just didn't know or didn't comply with the law as it was written. Calling it an Obama thing is misleading and inaccurate. Blame Gerald Ford. ITAR and ATF regs are wholely independent and have nothing to do with each other. They're separate, totally. Some things the ATF cares about, DDTC doesn't. Some things DDTC cares about, ATF doesn't. For example, if you modified a tail pipe to only fit military HMMWVs, you would need to register as a defense article manufacturer but wouldn't need a single license from the ATF.
The $2250 fee is the DDTC registration fee. You'd have to look up their current fee schedule, but it's probably accurate.
In short, it's been this way since 1976. Just most folks didn't know about it. More than a few gun trainers probably violated the hell out of US federal law by giving 'advanced' training to foreign persons (ie not US citizen, green card holder, etc) without an export license. Showing a person basic safety operations doesn't require a license. Providing tactical training does. I swear I should write a small book and sell it on Amazon.
What doesn't apply:
Painting doesn't apply. A lot of accessories don't apply. Simple repairs don't apply, mostly. Direct replacements don't apply (ie swapping barrels, triggers or stocks). Even swapping receivers may not apply. Basic assembly doesn't apply. Think assembling an AR15 from parts kits. Most AK builds would require an DDTC registration. Cleaning products generally don't apply. Cleaning weapons doesn't apply, generally.
What does apply:
Manufacturing any firearm parts. Materially improving weapons. Doing any significant (non-cosmetic) cuts by any means. Making ammo. Making changes to the weapon where you are increasing ammo capability, changing caliber, etc.
In short, 'light gunsmithing' doesn't apply. Significant gunsmithing does. If you're not cutting metal essentially or making new stuff, you're generally good to go. Only tricky thing is mods that increase ammo capacity or change caliber. IMHO, swapping AR15 uppers doesn't count. It's a one to one replacement, even if it's a different caliber. But modifying a barrel to take a different caliber would.
Disclaimer: I am not a lawyer. If I was a lawyer, I would not be your lawyer. Consult a export control and compliance lawyer before providing defense articles or services. This is meant to give basic guidance to provide general awareness, and is not situational applicable.