There is no apparent policy basis for the $250 reduction in the claim for the self-education expenses. Section 82A ITAA36 creates a set of comparatively complex rules and definitions that impact on the deductibility of self-education expenses. The view is that these rules achieve nothing apart from added complexity.
The aim it intends to achieve is not clear and nowadays the $250 is not going to go far in terms covering any meaningful expenses - it barely covers the cost of an average textbook. Moreover, the cost of capital items counts towards the $250 limit, even though the capital costs are not deductible.
As a history note: s82A ITAA36 was introduced at the same time that $250 of expenses of self-education began to qualify as a concessional rebatable amount under s159U ITAA36. The rebate was repealed from 1985 but s82A was left for no apparent reason.