Well, I'll chime in too, since I do primarily software/e-commerce work. Those numbers may be high or may be reasonable. It depends entirely on your idea. You say it's simple, but maybe it's not nearly as simple as you think. Is you idea "simple" like this: watch stock/commodity prices, map functions to the prices over time, and make smart buy/sell recommendations? That's not simple. I'd have to describe, in detail, the data gathering steps, the particular mathematical model you use to fit functions to the gathered data, and the criteria by which you make buy/sell recommendations. You might think it's all simple, but describing it properly can be very complex. Another example of something that might sound simple but isn't is collecting data about an insured through the Internet and applying statistical analysis to make a more detailed and accurate risk assessment.
Now, if it really is simple, those numbers are high. I've written applications pertaining to m-commerce adaptations of e-commerce processes requiring simple, yet non-obvious, adaptations. I've done some of those for around $6k.
The 50% number is wrong, in my opinion. In fact, it suggests to me a reason the cost estimate is so high. If a firm is looking at work outside their area of technical expertise, they plan to spend extra time on it and are less certain of its odds of success. I'll agree that it's much tougher to get software and/or e-commerce patents granted, but it works out in terms of time in the patent office rather than odds of getting out alive. For someone who knows what they're doing in this technical area, there's really no reason the cost should be disproportionate to the complexity of the invention and no reason that the mere technical field would dramatically affect the odds that you get a patent.
Of course, if the firm had made the estimate of cost and likelihood of success on the complexity of the invention and its apparent merits in terms of novelty and non-obviousness, those numbers could very well be reasonable. However, there's nothing so special about e-commerce that just doubles or halves numbers based entirely on the technical field of your invention.
Regards.