I did the same thing with eBay. The increase is whatever your market can take. If those who bought from you because your design was unique then no impact, they will still buy. If they bought from you because you were cheap, then they aren't coming back.
Simple example. If you have unique designs that are special to those who knit, knitters will buy. There aren't many people who cater to the "niche". You are not against 1000's of other people selling "It took me 50 years to look this good" etc.