just tell him since he's not good at building bicycle (if it that what you're saying), he'll end up spending a lots of money getting the bike shop to put it together for him.
tried that, i even worked it out for him!
think about it £165 frame + £70 wheels + £40 cranks + £35 for bar stem and post, £20 for brake callipers + £10 for levers + £25 for a pair of tyres + £20 chain and cog £10 for grips + £30 for assembly including bb facing, headset facing, Grease and cables = £425
tried that, i even worked it out for him!