The newer version of this (GS305) is on amazon right now for $15.99
Or here on Woot! today for $14.99.
The models are very similar and confusing. The 305 with dual link lights (similar to this 105 picture) also has managed features and is over $30. The 305 here is slightly cheaper than the 305 on Amazon, and this unmanaged 105 is a bit cheaper than the matching item on Amazon. Maybe the 105 is twice as much because it has twice the lights, or because it is blue.
The GS305 is the updated version. It uses less power compared to the GS105.
The Power Consumption of the GS105 is 2.7W (when all ports used, line-rate traffic)
The Power Consumption of the GS305 is 2.34W (Max) and 0.45W (Standby)
The 305 also has a limited lifetime warranty, while the 105 has a 3 year warranty.
And the 305 is made in Thailand, while the 105 is made in China and likely has something in it to track you until the planned take over.