A lot of the time, remappers charge more on newer cars because the car is worth more and they can get away with it. There are not that many parameters on a Ferrari 360, nor particularly large gains, yet everyone charges £899. Want to guess why?
At the end of the day Revo are using a generic off-the-shelf map, so any differences are irrelevant - they're uploading what they did on another car. I work in remapping, and I'd always want to pay for custom filewriting (and a good warranty) specifically tailored for that car/engine/mileage and what the driver wants.
Yes there are different parameters on some of the Mk5 models, but it's not as big a difference as they make out, and a Mk4 can take longer, that's just the way it is. I can't say I care for the sales gimmick either, a company should work out a fair price according to what they are doing and stick to it.
I would NOT be happy if I paid around £400 and someone with a similar car paid a third of that, for the same thing. And as the old saying goes, you get what you pay for, I would be reluctant to use someone who went for headline power gains which went beyond the manufacturers recommendations, and wondering what any guarantee/warranty they gave was worth if they did.
I rung round some of the people offering £200 remaps, 2 of them quoted more "because that car is not included in the offer" and one said that price was for a generic file, but for a £100 extra it was worth getting a custom file written! lol