Shimano's groupset hierarchy currently peaks at Dura-Ace 9000/9100, Ultegra 6800, 105 5800, all of which are 11-speed. They are followed by Tiagra 4700--10-speed, Sora R3000--9-speed, and Claris 2400--8-speed. The cost of the groupsets alone range from about $250 all the way to $2000. Let's not even speak of the Di2 stuff.

Then you have the previous generations of the same groupsets, some have the same number of gears, some have one fewer.

The general consensus among folks around here is that Shimano's 105 groupset represents the best value for the performance.

That should make it easier for you to compare different bikes. But keep in mind that the frame is also an important consideration. The Allez frame is a very well regarded one, so expect to pay a bit more.