Actually, I am worried about this shit getting amended kinda like how the hughes amendment got tacked onto the FOPA. That is a legit concern, which is why its critical to time it for the correct political environment. If the repubs get control of both houses of congress, theyd be able to tack something like this onto a "must pass" bill like the NDAA or a tax bill.
The $300 increase, imo, isn't too big of a deal, considering that 1. Inflation will eat it away, 2. You won't be paying it for suppressors and 14.5" M4geries, and 3. Wait times will be significantly cut down as the ATF isn't swamped. I think that a "compromise" like this shows that were willing to play ball (without compromising rights) as well as helps sway people who wouldn't care or are uncommitted antis, if we need a few dozen votes to tip the balance, and it puts political pressure on people to pass it, as it benefits other people than just gun owners.
Pegging the cost isn't a good idea because it'll linearly increase instead of a 1 time step. If we go up a fixed dollar amount, we dazzle stupid people with OMG 150% INCREASE FREE MONEY though that goes down to 200 2014 dollars in 20 years.
As much as I love the idea of reducing SBR/SBS to 10/14, I don't know if we'd be able to ram that through as its a way more noticeable change. With my 2" instead of 6" change, it feels like an afterthought and not something for opponents to focus on/point of contention, while still giving us carbine-length ARs. Ideally, if we have the congressional support for getting shorter barrel lengths, I'd agree that that is something we should go after. Maybe we can stagger it like having 1 bill for suppressors and 2" barrel, and then after it passes we do another trade for a 6" or 8" reduction (to 10" or 8" for sbr), and once people realize having that short of a barrel isn't a big deal (nignogs arent CCWing CAR15s) we can try to get it dropped entirely.
BTW, I predict that the ATF under a non-hostile admin would support this bill as it benefits them too to not be swamped handling suppressors and shit (provided they get money still). Having the ATF supporting a bill we're pushing would be really powerful politically.