Under promise and over deliver, is 1 of the best and efficient techniques / modes to win the customer for long rung is it really effective,if yes,why?

If a company who want to sell something with over promise and fails to deliver will always face impact of untrustfullness in longer run so to play it safe during last phase of Sale companies plays their card and they will promise things which is well in their limit and will add cushion on general scenario otherwise there are chances of fizzing out at the end moment so its always a good idea to "under promise" and then Over Deliver as its keeps customer satisfied and then the bond is strengthened and they can easily rely for future orders and supplies

over deliver  ll make customer to come again but under promise can give competitor advantage.  But too much delight of customer can raise standards and expectation . which ll lead to under promise next time but customer ll be loyal and ll give another chance.

'Under promise' and 'over delivery' are relative terms.

If someone makes 'under promise', then 'standard delivery' will seem like 'over delivery' with no price impact.

If someone wants to deliver more than 'standard', tangible price consideration is required (if applicable) because nothing is 'free' in business.

Both convincing skill & negotiation skill are instrumental in above cases.

It may not be the best but good & effective technique for short run and selective customers, i think. Applying same technique to all for longer period will not delight customers.