High Involvement purchase

It generally happens that whenever we plan to buy an expensive item,generally a high involvement purchase that we over spend or stretch our budget and take home an expensive item. why does this happen ???

Most research say that most of our buying decisions are taken at the store premises, Its the salesmen who plays with the consumers psyche, Think about it, how often has the salesman told you that Sir, this is only onetime purchase of your life? why compromise on it?

The consumer is confused and this solution for confusion is a high value purchase which he perceives as the solution and marketers have built over years that a high valued/priced item is of more superior quality. Hence a consumer ends up spending MORE !!