Amazon have run out of this set...but it was selling for £17.99 when I bought mine from there.
They now have this set available that has a lot more in it plus the limited run Ben case for £26
https://www.amazon.co.uk/Helix-Collector-Stationery-including-Limited/dp/B078GZBVGX/ref=sr_1_1?s=officeproduct&ie=UTF8&qid=1536317277&sr=1-1&keywords=star+wars+helix
I'd say yours would be the retail price or a bit lower...depends on someone wanting the complete set variations.