The affix ṭhak comes in the sense of 'its tax' after a word in the Genitive -6th-Case in construction.,
The word अवक्रय means 'Government-tax,' 'price,' 'wages,' 'rent' &c, coming from the root अवक्री 'to purchase.' Thus शुल्कशालाया अवक्रयः = शौल्कशालिकः So also आपणिकः, गौल्मिकः, आकरिकः ॥
Are not धर्म्य 4.4.47 and अवक्रय the same ? No. Dharmya is a legal due, and religious; while an 'avakraya' may be a tax exacted from a people by oppression, and so transgressing dharma.,