That's underpriced tbh.
I think I saw one shop sell the iEWB for 200kk recently so I think 240kk is not too high. I thought admins were going to continue with improved scrolls as event rewards for Valentine's so the prices could get bamboozled, so I sold mine for 120kk (or 150, don't remember now), but I definitely wouldn't go under 200 now because considering they literally gutted the rewards for this event, next even they'll either:
a) drastically reduce the chance fordrop of the improv scrolls or
b) won't add the iEWB/iEAC at all
And thus these scrolls are only going to go up with prices, because the demand will never go down and there's no way to rise enough supply to meet the demand. And as bsklakis2 said, China is more then ready to pay. btw. "They do not provide any security upon fail" it's irrelevant in most cases - when you have a BOP+8 there's basically zero difference if it will crystalize or go +0, because at that point the clean BOP is basically a consolation price (unless you have a special emotional attachment to it)
Also it needs to be considered that price of Energy of Insolence has gone drastically down as well. It used to be around 15kk, now you can get it for 4kk or even less if you buy, so the change for toi6 isn't that crazy either.