One thing in the story that doesn't make sense (SPOILERS)

There's not just ONE thing that doesn't make sense. There are MANY things here that don't. But, gee, all the CGI looks SOOOOO COOL, we shouldn't ask questions. ;)

I think the point was that the replicants born that way were more stable and less prone to violence and misbehaviour. Not to mention once the birth-roll started, they would be self-sustaining and he could simply collect the results of their work. Which is kind of how humanity in the real world works :) We are the good worker bees making a few select people extremely rich.

replicants reproducing on their own is much faster and cost efficient

the only plothole i have found is how K is allowed to have his police spinner after being suspended.

The fact that having replicants give birth would be more efficient than the current process is just a stipulation of the movie. We know its true because Jared Leto told us. Like you said, we don't know the details of the current process, and we don't know the details of how the replicants-giving-birth process would work either. We don't need to know these details, they're just part of the reality of the movie.

Let's speculate as a thought experiment. Let's say the current replicant-creation process requires lots of rare materials, big complex machines, very long delicate growth processes, has a high failure rate, etc. Maybe the replicants start out as babies and are aged and programmed within complex biological/machine devices. Let's say it costs $100 million per replicant and takes five years.

Let's also say that having replicants give birth would only cost a few hundred thousand dollars. Maybe the born replicants could be aged/programmed more quickly, reliably, and cheaply--we'll just say the birthing-replicants process only costs $500,000 per replicant, and takes only one year.

Of course, I just made all this up. Now they could have had Jared Leto make a speech to explain this (or something like it) in the movie, but that would have required a lot of boring exposition. There was no need for that. So it was just made very clear that making replicants by the current process is slow and expensive, and having them give birth would be much cheaper and they could create far more of them. Worked for me.

It could work....

you have to consider the scale.. the large numbers involved..

assume you start out with a population of 1 million replicants... to make an extra one is probably easy for your production facilities, but to make 500,000 extra ones would be difficult and costly... However, if they can reproduce they'll do that on their own, so your additional cost for 500,000 extra replicants is zero... the replicant parents provide for their owm... it costs you less than building one replicant!

As the numbers grow with time, it becomes even more compelling... Slavery works! (for the slave master)

If replicants can breed then their population will grow exponentially (as most breeding orgsanisms do unless checked by nature) and as they are so capable they will sustain themselves...

So if you want to colonise a series of new planets you just send thousands of replicants to each and come back in 100 years to find their numbers have multiplied and they've built sustainable towns and cities... So you can use your capacity to make fresh replicants to seed other planets, rather thsn wasting your capacity on trying to make each replicant in every city in every planet.

The world population in 1967 was 3.5 billion or so, it's over 7 billion now... that's in 50 years... So if we were replicants going from 100 to 200 replicants is only an increase of 100, so doable if you have production facilities for 100, but going from a billion to two billion would require a lot of effort andncost, whereas if they reproduce, all you have to do is wait...

However, we might be overthinking it... maybe he wants to do it also because he can! Because it makes him a god!

I think it has more to do with capacity than money. They can only make a certain number of replicants each year, whereas if they reproduced, they would multiply exponentially.

yikes, that plot sounds atrocious.