In Germany you can get unlocked USB-modems online starting from € 25 (= Huawei E160X, HSDPA 3,6 MBit/s incl. shipping) and The Phone House also sells unlocked USB-modems for € 30 in their local shops. Those are either K3565 (= Huawei E160X, HSDPA 3,6 MBit/s), K3520 (= Huawei E169, HSDPA 7,2 MBit/s), E172 (= Huawei E172, HSDPA 7,2 MBit/S + HSUPA) or K3715 (= similar to Huawei E180, HSDPA 7,2 MBit/s + HSUPA), which are all sold for the same price, allthough the two last-named are way better.
All these modems are Vodafone-branded and need a simple firmware update, which takes a minute, as the original access software (Vodafone Dashboard) won't connect to other networks than Vodafone's. So that's not a real SIM- or Netlock but a restriction in the access software, which can easily be replaced with Huawei's original software (Mobile Parter) by that mentioned firmware update.
I've started a thread on offers for USB-modems including debranding guide at
Der UMTS-Stick und -Datenkarten Schnäppchen Thread - Telefon-Treff (read thread completey as prices were updated several times).