Pitched v Flat roof - Cost comparisons

[Skyedriver]

I know pitched roofs are more long lasting and almost always more aethetically pleasing and fit in with the house more readily and if I had loads of money it would be a tiled pitched roof on the extension I am intending to add to the new bungalow we are purchasing.
The extension is around 3metres x 8metres, and sits on the side of the bungalow. Others on the estate have gone flat roof but I want to do this once and right, cost permitting.
The pitched roof could T into the pitch of the bungalow and could go in at the flattest gradient allowable 22 degrees (?) and at 450 c/s I would only need 7 trusses plus a few other bits and pieces. Insulation would be rolls of f/glass rather than Kingspan which might be cheaper too. Plasterboard ceiling the same. Other cost considerations but I can budget for them (simple Velux roof lights rather than a pitched glass skylight but I can sort them costs).

So in general what are the cost differences, my guess is twice as much but am I underestimating drasically and what would it cost to construct a built up felt roof at that size.

Thanks everyone.

[Skyedriver]

I know, had them before but there is so much to do and budget is stretched a bit. Tiles is a "fit and forget" it's just the cost situation. If its only a grand more then great if its ten grand more then I need to forget the windows, boiler and sell a kidney.

[Skyedriver]

Thanks guys, been around the estate and others today and the pitched/tiled rof looks so much better although everyone on the estate our new bungalow is on seems flat roofed, every one a different design.
Oh and Mr Maggit, sorry, the new place is in N Yorks, but still keeping our Skye home. Couldn't sell it too many memories.
Anyone need a kidney or right arm?