What level of management do you require?
You may find some hosts can bundle things like security updates etc into their standard price however if you're going to want them to spend time configuring new sites, dns and all other little bits and pieces you should expect the monthly costs to increase appropriately.
Hosts can't provide quotes in this thread and so this example pricing shouldn't be taken as one from me however I'd estimate that for good quality hardware (i.e. a solid machine costing £1500-£2000) and reliable transit along with basic management you should budget around £300-£350 per month. Is this roughly what you were expecting?
I'm sure once you hunt around you'll get budget hosts offering pricing less than this and some hosts coming out substantially more expensive however it's probably a decent ball-park to work from.
If you have any questions feel free to shoot