I currently have a piece of crap mp3 player. I bought it for $12.99 so I can't complain. It's been an okay player except for the fact that the battery is inconsistant. I would charge it for a few hours only to have it die on me again after thirty minutes of use. Sometimes it charges and sometimes it doesn't. It's all a gamble. I require this mp3 player to work for me while I'm at the gym because they play that easy listening crap at the gym and it doesn't motivate me to lift heavy.
Im also looking for one as well, because my current MP3 (Sony walkman A series, 50hrs of battery life) i bought about 4 years ago is starting to die out. [BTW this is not being produced anymore, so you wont be able to get it, unless you go for 2nd hand market]
The reason why your player dies out quickly, is (my speculation) because you put the sound on quite loud, don't you? In which case, even if you buy a new player costing $20-30, it would yield the same results.
If I were you, I would spend significantly more than that for an MP3 player. Its better to pay for a player that would last for a longer time (2yrs or more) than having to buy cheap ones every year or so.
Having said that, I would recommend SONY walkman series, iPod shuffle, or one of the COWON series [ although im not too sure about their products, but seems to get good reviews on it] for cost-battery performance.