The most common shatnez problem found in men's wool suits is linen interfacing in the collar.  This kind of shatnez defect is easily remedied.  At the request of the customer and for a charge of $15 the shatnez checker will remove the external felt and the attached linen in such a way that it can be used as a pattern for the replacement.  The checker will also furnish a new piece of felt and a piece of non-problematic interfacing.  This Houston tailor charges $28 to replace the collar.  It is important that the checker himself remove the collar in order to insure that all vestiges of the linen are completely removed. 

The dark gray material below is the external wool felt; the light brown material sewn behind it is pure linen; and the slim white line of fabric is the collar fold reinforcing tape.

Some garments are simply irredeemable, because the shatnez is located in places that would damage the garment if removed.  That is not to say that a tailor couldn't remove it, but it is beyond the ability of the shatnez checker.  Such an example is this Aquascutum wool-blend raincoat.