Yes, honey is expensive. It makes great mead but I see no reason not to use cheaper sources of sugar. That flow hive looks great. And you'd have the satisfaction of knowing that you're adding some sorely needed pollinators to your environment.

With regards to cheap sugars for fermentation, keep in mind that if you fall back on to a sugar source that produces a less than desirable fermented beverage, you can always distill the alcohol out of it.

On a semi-related note, since you have means and oppurtunity, have you looked into hugelkultur? I started it in Florida and it seemed to work very well. I've also done mini versions of it in very small containers. It's such a simple concept. Links below:

https://richsoil.com/hugelkultur/

https://en.wikipedia.org/wiki/H%C3%BCgelkultur