kiwijunglist: $300 sounds like heaps. Duct should be $50-100 and vent should be $25-50.

It's difficult to say without knowing exactly what is required and the purpose. Anything non-standard tends to get expensive quickly.

I'm assuming this is purely for venting outside, in which case non-insulated 200mm ducting would be all that is required. That's around $12.65 for 3m at my local sheet metal dealer. Solid spiral tube is $19.55 per meter.

If he needs solid bends or round to rectangular adaptors etc., it gets into the hundreds very quickly. I ended up making a round to rectangular adaptor as it was cheaper for me to DIY out of foam and fibreglass than it was to get someone to make one out of steel, and similar in price to purchasing an off-the-shelf adaptor that wasn't quite the dimensions I needed.