Hi there,
I have searched the forum, before posting. There is no similar thread.
I have gone through the forum and made a list of inexpensive knockoff wifi adaptors that people are using. I'm not able to make out which one is the most preferred now.
Hope this will help others to choose one as per there requirement.

discussed here www.backtrack-linux.org/forums/showthread.php?t=31309 It has RTL8187 chipset. Reviews are perfect, but I'm not sure whether it is still in demand as that last review in the site is dated 9/5/2011.
Price : 21.70$

It has the longest antenna among all. It uses RTL8187 and has a maximum range of 2-3 kms as claimed by people.
Downside of antenna - As per the reviews, it is 1000mw actually and antenna is 5-8 dbi rather than 10dbi, base can't support the antenna. Few complained that the antenna is not of good quality and they used other antennas like this one, this one and this one.
I'm quite sure, people are buying this, as the last review is dated 7/23/2012.
Price : 17.90$

There is no review or rating for this adaptor. As per the specs, it uses RTL8187 and claims to be 48 dbi.
Price : $18.20

Price:$ 23.80
Last review dated 01/22/2012.
Chipset can be of RT3070L / RT2870 / RTL8187 .

discussed here -> http://www.backtrack-linux.org/forums/showthread.php?t=33740
This is fancier than others with 2 antennas, but not sure about its efficiency.
Price:$ 21.20
Last review dated 05/29/2011.
Chipset RT3070L.

Similar to previous one, this has 2 antennas, but little pricey. Reviews are recent.
Price:$ 26.20
Last Review dated 07/05/2012
Chipset : RT2870

Please let me know which one do you prefer as per your experience with that adaptor.

P.S. - I'm not linked to DX in any way, just seeking some help here.