As a General Rule, I never deal with any sellers that ask for contact outside of ebay (especially if the email is in the listing, and not something you do thru ebay) since its 99.99999% a scam (theres always a chance that the 0.000000001% is someone who cant use the ebay system).
But I wouldnt be surprised if certain items go for real cheap, half the time its because they did not put it in a well traveled category for the types of goods listed. Others could just be simply lack of keywords or not properly spelled. Sometimes you can get a good deal if you know what to look for. You usually gota be weary of the ones where there from people who playing dumb, like they say "yea, my dad gave me an RZ67, and I'm not sure if it works , but seems to be ok" where they claim ignorance, which half the time means theres something broken with it, and by claiming ignorance you cant scream as much if it come broken, or it also fuels those who think "man, this guy doesnt know what he has ,I think I can get a good deal on it".
Oh also if yer really bored, you check their recent sales and buys, its a big red flag when someone either.
1) has 40 sellings of 99 cent items.
2) many buyings of 99 cent items.
3) only feedbacks come from another account and only that account.
Then all the sudden a high dollar item.