Where to start.
* Pistol - Ok a 250-300 dealer.
That's not dealer price on a glock.
All of this "custom" work is unnecessary, worthless and come from the factory standard.
A grip reduction comes standard from the factory? A trigger job comes standard from the factory? A lot of people who are serious users do some these mods they are not all without benefit. The issue to me is more the price they are asking for some of it.
* Carry Bevel Slide - its not like they are thin who cares. Plus new holsters are going to be really hard to find.
You are not going to need a new holster you beveling not dramatically altering the shape or dimensions. Based on your comments I'm curious if you understand the purpose of this modification and what it entails. My 26 is already rounded more than my 19 and neither are uncomfortable to carry. Its not a bad modification but not one I need. There's not a lot of sharp edges on a glock.
* Scallop Frame at Mag Catch - Why?
Some people find it to be of benefit in getting to the mag release. I see nothing wrong with this mod per se and particularly not if it makes the gun more usable for the shooter. Even if it adds a lot in function it is a $10 mod at bowie tactical.
There is a lot of room to critique that pistol at that price so no reason to stretch to silly critiques.
I see some of those mods as being useful others as being rather superfluous.
I would modify the frame: Grip reduction, under cut the trigger guard, round the trigger guard, 360 degree stipple, stipple the frame flats. However one can do it themselves if they really like or pay a couple hundred for it do be done very competently. Bowie, bore sight, etc will do this.
Paying someone to make any of my glocks "more reliable" would be as silly as flushing money down the toilette. They run very well as is and I don't see those mods offering any real value.
I see no practical value in recrowning the barrel on my glocks. It might have benefit on paper but given how I use them and what I need them to do, I see nothing that would benefit me in the real world. In fact I would rather spend the money on a threaded barrel.
Personally I'm not a fan of front cocking serrations. I wouldn't have them put on my gun if it was free.
I personally run a stock trigger on my glock but trigger work could provide benefit.
The sights are a good upgrade but you don't need a premium price gunsmith to install them.
In sum, there are some worthwhile mods there, others that are "going the extra step" one could say. The real issue to me is that you can get the work done well for much less (and just the parts of it that really offer something for even less). Of course if a shirt doesn't say Versace you can get it for much less too. In the end the price is what the market will bear.
I would modify a Glock to be a more useful pistol to me but no that pistol is not worth $1700 to me.