S. R. Faruqi:

The wordplay among saudaa))ii , bechte hai;N , paa , sar is clear. In the second line yih kuchh has been used with extreme excellence, because the tone is that of conversation. But the thing that's being said is uncommon. On the basis of yih kuchh , an ironic tension has come about in the verse. There's also the affinity of chalan and paa .

[See also {42,4}.]

FWP:

SETS == DOUBLE ACTIVATION
MOTIFS == COMMERCE; MADNESS
NAMES
TERMS == WORDPLAY

The conveniently identical spellings of the Arabic and the Persian words saudaa (see the definitions above) make this word an obvious and irresistible trope for the ghazal world. One can be a mad trafficker, and/or one can traffic in madness, and who's to say which? In the present verse, both possibilities are fully activated. Commerce or madness, madness or commerce-- back and forth we go, forever. For another such example, see {877,6}.

Is it possible to 'sell' something for 'free'? This would seem to violate the transactional definition of 'to sell'. But then, it would become just one more form of saudaa))ii , 'madness'. The speaker's helpful but clumsy attempt to explain it ('this is some such thing that they do there'), and the businesslike use of chalan , add to the incongruous pleasure.

Note for grammar fans: The first line construes the addressee as a familiar person, since the ho shows that the omitted subject is tum . (Unusually, tum ho can be either 'you are' or the future subjunctive, tum ho from tum hoge .) Then the line goes on to use a polite imperative verb. This sort of mix-and-match happens in colloquial speech.