The affix ṭhak comes in the sense of 'who takes' after the words 1. pratikaṇṭhā 2. artha and 3. lalāma being in the Accusative -2nd case in construction.,
Thus प्रतिकण्ठं गृह्णाति = प्रातिकण्ठिकः ॥ So also आर्थिकः, लालामिकः ॥ The word प्रतिकण्ठ here is an Avyayi-bhava meaning कण्ठं कण्ठं प्रति, and not प्रतिगतः कण्ठं = प्रतिकण्ठ, for to the latter no affix is added.,