That one's a clear answer. Buying a hard copy from a store loses Take 2 the printing costs and what the retail store takes. Selling as download for the same price means turning all those old costs into more profit. That is, on a $40, T2 might make $15 per disc sold, with $10 going to MS and $10 going to retail and $5 on printing and distribution. On the same game sold for $40 as a download, they'd make $30, pocketting the money saved from printing and selling to stores, bar whatever extra cut MS make.
A hard copy has some advantages over a soft copy, such as Todd33's much valued post-use worth. If you're not getting those benefits, the publishers are 'milking' the service to get more profit from it. Ordinarily download versions of software are cheaper. If T2 pass on savings to the consumer, it'll be a case of everyone benefitting. Except the retail chains and printing firms!