DIY vs. ASP

One of the things we are evaluating at work is going to an ASP (Application Service Provider, or outsourcing it to someone else) model for our online e-commerce activity rather than DIY (Do It Yourself, AKA Adolph makes it up as he goes, doesn't do a bad job of it, and saves the bacon now and then). One of the large disadvantages of the ASP is that the transaction costs are high: 5 to 6%. Our own effort costs us 2.5% and some of Adolph's effort. Our effort doesn't has as many bells and whistles, but those could be added.

The significance of the additional 2.5 - 3.5% is that most of our fundraising comes from events and an increasing amount of that activity is online and would be subject to the ASP transaction percentage. If we are an "83 cents on the dollar goes to our mission" organization, would the additional 2.5 - 3.5% mean we are an "80 cents on the dollar organization?" Would the bells and whistles grow something faster than its natural rate of growth? Would it be worth growing if we were a less dollar efficient organization per fundraising dollar?