I've always owned off the shelf keyboards and I think it's time for a change.
Why?
Not being rude, seriously, why do you hope to accomplish?
If it's a special layout, fine. If you're wanting it for "coolness" or internet points, I'd stop and ask why that matters and lastly, what is the end result you hope for. If this is to be your daily driver you may want to consider sticking to off-the-shelf. Customs are not necessarily better, they tend to have less tested, less warranty, and once out of production can mean trouble finding replacement parts if something goes wrong. There's nothing wrong with wanting one, just keep in mind it's kind of like a show car, every scratch devalues it, a problem can mean a very costly repair, if it can be fixed. If you break a Cooler Master you can replace the whole thing relatively cheap but you also may be able to get a replacement part from them, the same cannot be said for a limited run custom.
I'm not saying customs are better or worse, just that they come with different problems.
I'm just not too confident in the whole soldering thing so I have a few questions:
Soldering switches in is dead simple, de-soldering is where it gets a bit more difficult (depending on skill and equipment). If you're buying a board without switches, you can do it yourself pretty easily in a few hours, there is plenty of guides and the equipment you need is pretty cheap. You don't need a Hakko to assemble a board, in a pinch I've soldered using irons I bought at a dollar store and even hacked together makeshift irons.
Of course just installing switches means buying something devoid of switches, but if you are going to contract this out anyway it doesn't matter much.
* Anything I should note about my first ever "custom" keyboard?
Feel free to enlighten me on anything. I'm really interested in getting to know this stuff 
You call it an "insane amount" and yet you aren't willing to do it yourself.
Soldering can be an hour for switches in a small board or several hours if you make a tiny mistake. De-soldering is tedious, (a little) risky (to the board and switches) and can take several hours. You say it's expensive but this is (somewhat) skilled labor and desoldering often involves special tools they had to pay for. If you think that's bad, try opening 100 teeny tiny switches, brushing expensive lube onto teeny contact points, putting them back together, ensuring everything works, and then soldering them into place. Most of it isn't difficult work, especially if they've done it a lot but it's still specialized and more importantly, tedious work. After all that they still then have to repackage it and ship it back to you, multiply that by your hourly rate. Are they still asking too much?
The cost of a person to do what you want is
their time and labor, it is not tied to
your end result, learn to separate the two.
(Everyone is guilt of this at times, I'm not trying to bash you for it)
