Paul Graham sums it up:

Startups worry far too much about people copying them.

First of all, it will take competitors a long time to realize that your idea is even a good thing to do. It seems obvious to you that your idea is good. You had it. Other people will take longer to see that.

Especially big companies-- as anyone can attest who has tried to convince a big company of something obvious. Often big companies don't want to see that an idea is good, because they already have a lot invested in some other plan.

Even when competitors realize your idea is good, (a) it will take them a long time to implement and (b) they'll probably screw up critical things.

And finally, working on your ideas will lead you on to new ideas. So you'll be a moving target; by the time competitors copy what you're doing now, you'll be doing more.

A lot of lawyers who want to implement some form of value pricing or flat-fee billing in their firms are reluctant to do so because they believe their competitors will just swoop in, copy their pricing model, and then undercut their price.  My advice (and Paul Graham’s) is to stop worrying about that and just do it.  Once your competitors realize just how good your idea is, it will be too late.