The most important thing for the skilled worker is to know his/her skills and work are valued and appreciated.
There are many ways to make employees feel appreciated if wage increase are not always possible. Creating safe, friendly and encouraging environment can help them feel secure witch will increase their confidence and as a result - productivity. Encouragement can be either tangible or intangible. Tangible - it can be employee appreciation breakfasts or just simple bagel or doughnuts in the morning - occasionally or on certain days of the week. Intangible - could be all kinds of awards and acknowledgement in various skills/field sets.
For friendlier and more comfortable environment - there can be certain relaxation area in the office , that will let people recharge and get back to work in refreshed state of mind.