Feedback is one of the most important ingredients for any company.
Because everyone wants to reassure that they are moving in the right direction. I was reading a book regarding lean startup where the writer invited many guests to physically visit their office and tried to influence them in using the product as well as to share it with their friends. Merely asking the invited guest to share the product helped the writer to understand the reaction of that person which matched with many others who were invited in the same way.
Feedbacks provide surviving or guiding insights for the company, but what is in for the invited people? they have spent time and maybe some money for coming in and even if don't like your product, it still counts as an insight.
Adding rewards for providing honest opinions attract users as they feel that they are doing something productive rather than just advising for the better good.
But I see a lot of companies try to trick people who are willing to provide feedback for some rewards, leading to less number of audience who are willing to spend precious time to provide feedback even if there are rewards associated with it.
You are cutting your own legs if you are tricking people for feedbacks.
Best strategy would be "Don't promise anything" or promise a decent reward.
For example, you are the first person to manufacture fidget spinner and want to know if people will play with it or will throw it away.
Starting with prime target audience with age group (12-18)yrs
Reward - 3 Fidget Spinners.
A little beyond your target audience age group ( 34-30) yrs
Reward - 3 fidget spinners and 2 movie tickets (with popcorns).
Hence, merely adding some exciting rewards won't cut it. Promising i-phone to one of 100 people will get you 99 angry guests at the end but for the same cost if you are able to provide 100 people with your product and little but useful incentive then hallelujah you have 100 happy guests willing for more feedbacks in future. In addition, 100 people have your product which they will share with their relatives and friends.
It totally depends on how you are strategizing your surveys to get more benefits out of them.
Adding rewards with the survey will definitely get you more attraction but to build upon it, you need to think what the rewards should be.