Not that I need one right now but I am curious how much they will sell for. I purchased a good quality micro-SIM cutter several months ago that works perfectly and cuts mini-SIM's down without any problem. It was about US$3.50 on eBay and I understand nano-SIM cutters are already appearing. Might make more sense to get a cutter if T-Mobile's prices are more than the cost of a cutter. SIM thickness does not appear to be an issue from tests people have done.
At this time, I have a Sprint locked iPhone 4S so I have no need for a nano-SIM. Still it is always good to plan ahead just in case. The bigger problem for me will be getting Sprint to completely unlock my iPhone next October when the two year contract is up. So far they have been telling people who have paid the ETF or otherwise completed their contract to go pound sand. Much like AT&T was doing until April.
No loophole, It's been that price for a year. It went up to the regular $6.99 price for a few weeks awhile back, but then quickly went back down to $0.99 and has stayed there ever since. It's now considered the regular price by most.