I’d say marketing. Are colonies easy to sell in the UK? I guess anything’s easy to sell at a price.
I have a lot of unsold nucs with winter approaching, which I intend to use to replace some under performing hives. I made a heap of slatted racks, which I’ve nearly finished painting. I’ll swap the colonies over while I’m installing them. That’s an advantage of a flat roof, with nucs sitting on top of them. Simply take a hive away & drop the nuc down to replace it.
Some commercial company willing to buy from local beekeepers at the low price and they sell making the profit. I directly market my colonies, and people who come and train with me all enjoy the calm nature of my bees.
I teach beekeeping to beginners and some in the end want to purchasing my nucleus colonies which makes it easy to have a one stop shop.
There is usually a high demand of Wintered colonies in spring, you also get the best price for this.
What is it like where you based
Hi Paras, I market mine as well & people are also impressed with how quiet my bees are. I get a lot of referrals from our local bee club, plus other referrals & repeats. I did a little bit of teaching but find that people don’t absorb the info, so I stopped doing that. I try to encourage folks with Flow hives to join this forum, however so far no luck.
I only took up teaching people since some clubs were not supportive of the FH, I have been very successful with FH in my area and I too get a lot of referrals since I am the only one rearing Langstroth Nucs in my bee club.
This may be a bit off topic but can anyone tell, what is the maximum water temperature I can use to clean the flow frames before I store them over winter.
70°C according to Flow. 
I don’t clean the frames after the season the bees clean them dry before I store them.