My main gripes with Machester are parking fees
I've been using Manchester for over 20 years now and this has never been an issue. If you're willing to book at least a few days in advance, Manchester has some of the cheapest on-site and off-site parking in the country, especially the latter. It's peanuts compared to the London airports or even Liverpool. Last month, I paid £25 for 8 days parking at Jetparks, which is airport owned and takes less then 10 minutes from car park to terminal. That would have been easily double and probably more at Heathrow.
If you turn up on the day and go in the multi-storey, it'll be a very different story of course.