Just saw these and bought one - cheapest i've seen them in the UK (£12.59) without a sale/ special offer, free postage as well:
https://www.amazon.co.uk/gp/offer-listing/1616619953/ref=dp_olp_new?ie=UTF8&condition=new
My swarm is now up to the required 8!
Cancel cancel... within 10 mins of posting this they were no longer there... 
Did you also notice that pretty much all shops have now increased their prices. Whether this is due to actual price increases or Brexit I'm not sure but it does suck
I am on the other side of the channel and just checked few online stores - prices are largely unchanged, 15,95€ per CR 90.
Also checked if 12,59 GBP would be a great offer at all, but even with the loss from Brexit the rates are still terrible.
Now, my british comrades, if you could vote for a few more questionable decisions to utterly destroy the GBP rate, I would happily share all those CR 90s with you ;-)
Did you also notice that pretty much all shops have now increased their prices. Whether this is due to actual price increases or Brexit I'm not sure but it does suck
A price increase has been in the pipeline for awhile it has nothing to do with Brexit, and yes it certainly does suck.
Now, my british comrades, if you could vote for a few more questionable decisions to utterly destroy the GBP rate, I would happily share all those CR 90s with you ;-)
Will choosing Boris Johnson for Foreign Secretary suffice?
Andrea Leadsome for Environment secretary should put the nail in the coffin...
I imagine its just Amazon's algorithm. If noone buys it is reduces price, until demand goes up again. Hence ISDs having a low discount compared to VSDs.