It seems most of your question has been very ably answered by others, but just to show I’m not ignoring you:
As FRANK_CADILLAC has said, there’s a limit to how much you can build in your base. Each item you make, including plants, has a numerical value. Once that value reaches 2,000, you can’t build any more.
(I was going to link to DevilinPixy’s list of costs - but I’ve been beaten to it).
That’s why designing a good, profitable base is so tricky. You have to specialise in one profitable product, then concentrate on growing only the plants that are needed to make it. You have to find ways of growing as many of the right plants as you can, whilst at the same time using as few building materials as possible.
You also need to consider the conditions on the planet you’re building on - some plants will grow outside, but only in the right climate.
My personal preference is to completely remove all my base buildings, and start right from the beginning, concentrating on maximising growing space, while minimising building costs. It’s expensive, and it takes a bit of planning, but if it wasn’t a challenge, I wouldn’t enjoy it so much.