Most of the nucs I sell sadly, are destined for a certain death and strangely, it is often the beek selling them that gets the blame rather than the incompetence of the new owner. Also you only have to read on here the approaches that some take to managing bees means there will be a high level of demand pushing prices up. My association insists swarms are collected and surrendered FOC save for the replacement of frames and foundation and sold by the club for £50 that perversely, undervalues the bees to dangerously low levels by the new owner. Suffice to say, I dont participate. TBH the real problem is how we teach new beeks the craft. I know, I was one once and looking back, I'm a little sorry for those poor bees.
I'll have about 20 nucs to sell soon round the £220 mark and personally I will sleep well at night with that being a reasonable price in the full knowledge I could and perhaps should charge more, if only to try and avoid the almost certain death sentence the sale will often mean.