I'd get custom PC boards made for anything more than 5 or 10 boards, or for anything you are going to sell. It's more "professional", and the labor savings will make it worthwhile. Even If you are building the circuits yourself and the labor is "free", it might take you a year to build 1000 breadboard assemblies. (And, there will be more to "production & test", than simply assembling boards.)
I am brand new to hardware programming
If you are building 1000 of something it would be a really good idea to get some design help & guidence from someone with experience. As a minimum, open-up some of your home electronics to see how it's put together & wired. You'll find one or more PC boards in everything.
Typically, you'd build one or two prototypes. That's one step closer to the final design. Where I work , we skip the breadboard and go straight to a prototype PC board. (When you are paying labor to build a breadboard, it's faster & cheaper to skip that step, even if you have to make the board twice. In fact, at a minmum, we usually have to make a few "cuts & jumps", and re-layout the board with the corrections before going into production. And, sometimes, we can't make the PCB to work and it has to be re-designed.
We seind our boards out to an assembly house to have them assembled (even if it's 5 prototype boards). They have the automated equipment (and skill & experience) to make a good (and good-looking) assembly. Automation is the only way to make a "nice" surface mount board assembly. We are a small company with many different products. In production, we typically send-out "kits" of 25-100 boards. Like anything else, the more you do at once, the lower the unit-cost.
Basically, you want to make your prototype as close as possible/practical to the final product, except for where mass-production techniques are not practical. For example, you might use an off-the-shelf cabinet with rub-on lettering instead of a custom manufactured cabinet with silkscreening.
Then before going into full production, you'd make a pilot run of the "final" design. This is your last chance to check-out the design & production (amnd possibly make final changes) before going into full production. Typically, you'll have some extra PC boards left-over from the protototype, since a small quantity of boards is about the same cost as one. If all goes well, these pilot-run units can be sold or used for beta testing.