i4's are usually super expensive because they come in "special editions" and patterned versions and annual versions. (all cosmetic differences) Best thing to do is look around a bit and you'll find i4's from a previous year or whatever.
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http://www.store.justpaintball.co.uk/masks-goggles/dye
You can see the i4's at the top in JustPaintball are £90 because it's an older pattern, the standard, non-pattern ones are £100 and the new 2015 colours are £110
Virtue Vio's feel pretty similar to i4's in size and weight but are around the same price.
V-force grills are good, Empire E-flex, proto pro-axis...many more. All good masks, you need to ask some other players nicely to try on their masks to see what you like before you look into buying anything you haven't worn.
Cheapest mask I can recommend you that is still really good is the JT Proflex, old design, but still used for a good reason. Really nice, lightweight, well ventilated mask for around £50[/QUOTE
Cheers mate that's incredibly useful. I will look into all of thee masks that you mentioned