Now the actual cost to be paid by the customer is apparently displayed - I say apparently because I am still a bit confused by the information.
In the above screenshot, one day of usage of the iPhone data plan is shown, resulting in ¥744 worth of packet charges (9,300 packets). At this rate, the maximum price for this particular data plan (¥4,410) would be reached in about a week. Previously, the site would continue to show charges increasing above the cap, which would reach around ¥20,000 by the end of the month.
The individual packet charges are subtracted, leaving only the charge for the flat rate plan displayed (¥4,200 * 5% tax = ¥4,410). However, this person has only used 9,300 packets,
Here is another shot from a different user illustrating the same thing. Also, notice the flat rate price for the previous month seems to be prorated, which also doesn't make sense since the user consumed well over 71,250 packets.
The below screenshot provided by an admittedly heavy users shows one day of ridiculous usage under Softbank's old way of displaying current charges.
Someone who followed all the directions properly and just slid an iPhone or other Softbank SIM card into their overseas smartphone would be right to panic when seeing this information - especially if they were not so comfortable reading Japanese and didn't notice the fine print (not shown) saying this is the price prior to any discounts.