I just checked mercado libre. There are thousands of used phones for sale. It all depends on what you consider relatively inexpensive.
I have a Moto G 2nd generation 3g phone with a 5" screen. There are new ones available on ML for $3000 pesos. There are 3rd generation 4g Moto G smartphones offered at $4000. The second generation model has an 8 mpxl camera and the thrid generation has a 13 mpxl camera.These prices are significantly lower than they were a year ago, but they're probably double the best prices you'll find on amazon in the US.
I like the Moto G because it has the "Gorilla Glass" screen. I use a protective case as well. I've only dropped it once and the glass did not break.
If you don't like Motorola check out the basic Samsung model with 4g and a 4.3" screen for $3000.
http://articulo.merc...-libre-gtia-_JM