RIM gave the impression when it unveiled the BlackBerry Curve 9320 and 9220 that its lowest-cost Curves were doubtful prospects for the US. Thankfully, that's been proven wrong by Boost Mobile, which just launched the 9320's CDMA cousin, the Curve 9310. The message-manic BlackBerry comes to Sprint's prepaid network with its BBM key intact as well as BlackBerry 7.1, a 3.2-megapixel camera and that all-important low price: at $100 contract-free, it's one of the cheapest ways to leap into smartphones in the US. To top it off, Boost is throwing in a very tantalizing BBM Unlimited plan. The deal offers unlimited calling, text messaging and (naturally) BBM; although it starts at $45 per month, it gradually dips down to a very reasonable $30 per month if owners pay their bills properly for six months. Both the Curve 9310 and its companion plan will be available July 10th, giving us time to find the needed spare change under our couch cushions.