I'm on the frugal side. In fact both of us are. Our original koi from 9 years ago were 3 for $15 at a local farm stand/greenary. A couple years later they went up to 3 for $25. Most are butterfly with some that are very nicely finned and colored. Any others that were added were less than $10, closer to $5. To us they are as precious as any.... even though they are not purebreds.
They all were bought small, usually only about 3".
So, in our view, you don't have to spend big bucks to get enjoyment out of this hobby. And if you buy your fish young, they won't cost too much.