Dealers don't give exact valuation of your car as they have to share part of exchange bonus with the company.I myself had this experience with tata dealers today,they calculate value of car including exchange bonus.But when you compare market value of car with what dealer is offering it is very less.
Rightly pointed out by Mr. Arora - some car makers have exchange schemes wherein some part of contribution of exchange discount - normally 50% is shared by dealers
As Kuldeep, in your case it does not seems exchange - dealer is hence offering you 10K Cash + Rest 15K as package. See if you can stretch more on cash offer - but still its a descent deal . All the best !!