Telecompaper has it that the Allegro will cost only €299 - this would certainly make it one of the most affordable Mango handsets on the market.
Although Acer didn't confirm this, I assume the Allegro is the previously spotted Acer W4 (pictured below). If that's the case, the handset features a 3.6 inch WVGA display, HSPA, Wi-Fi, GPS, 1GHz single-core processor, and a 5MP rear camera.
Acer has also announced that the Liquid Mini Ferrari Edition (which we've already seen) would also cost €299. The Liquid Mini Ferrari Edition runs Android 2.3 Gingerbread, and features a 3.2 inch HVGA display, 5MP camera, 8GB of internal memory, and a 600MHz processor. It should be out before the end of the year.