Mark is right, except that the cost looks about right to me, they aren't that hard to replace. However, they hardly ever wear out. They have very little movement, so very little wear. It is also very difficult do determine if one or both are loose, certainly not something that you casually notice while changing the oil.
What I would suspect is that the bellows that protects the steering rack and the inner tie rod ends have split. This is about the right age. If the inner tie rod ends are in fact worn out, then these bellows should also be replaced whether split or not. Now a split or torn bellows is something the mechanic would have noticed while changing the oil, and if they are, they need to be replaced. If not replaced, dirt will get into the rack. The biggest threat is to the rack itself rather than the tie rod ends, but the rack is a lot more expensive too.
Ask your mechanic again if he really things you need the inner tie rod ends or just the bellows. Ask how he tested the inner tie rod ends. Just because the bellows are damaged, it does not mean that the tie rod ends are.
If the mechanic wiggles the wheel and you see the rod move in and out a little, see if the wheel on the other side is moving too. If the wheel on the other side is moving, then the tie rod end is good. If one wheel is wiggled, the other should wiggle exactly the same amount.