How to use marketing in such an effective way so that to get positive response from buyers to price changes or hike in prices?
You could send out an email to your mailing list with coupon codes offering discounts for customers who have purchased your products in the past.
I used to have a website where I would sell herbal supplements, and in order to win over customer loyalty, I would send people at least double what they ordered on the first sample, and I made sure to be very generous with other orders as well.
My margins on this were really high, so I think the loyal customers increased my profit more than the extra use of ingredients hurt it, but this was certainly an effective way of making sure my customers returned and told their friends 
I also gave an affiliate code to anyone who would take it. People like to be rewarded.