i purchased an escort cosworth about 10 years ago now and it's worth a fair bit more now but it will never be a life changing amount.
better off buying an rs car to use and enjoy and not worry about its value, if you intend to use it as a daily then wear and tear will be factored in also.
prices could still fluctuate as they seem very high at the moment and I would be wary of buying a car for top money in the current climate.