I want to buy some good quality alpaca clothes as gifts. Are there any places in La Paz where I can get them? What sort of price (on average) would I pay for a sweater? Many thanks.

Shops on Calle Saganarga, the goods are made for tourists, so you pay a little more, but you can find good quality and bargain firmly, and you should be able to get some good deals...enjoy
Just be careful, we were at an alpaca warehouse store just out of Cusco and the shop owner spent some time showing us the different grades of alpaca items, and I couldn’t tell the difference between the more expensive real 100% pure stuff and the almost all synthetic items (also with 100% pure baby alpaca label on them). This was even with them side by side.
I’m not sure if you can do a burn test on it like with silk, ie burns or melts, smells like burning hair, ash residue etc.

you can do a burn test but I wouldnt recommend doing that to the jumpers in the shops as the owners get quite irrate! Prices range vastly depending on quality and your bargaining skills but you can definately get some bargains. You can also buy balls fo alapca wool but it isnt easy to find. Avergage price for a jumper - from 5us$ to 100$ depending. I have bought nice mens jumpers for as little as 70bols though (I bought 5 at once to get that price for xmas pressies) - though 120/130 Bols is a more normal price.
I don't know any nice men to buy jumpers for but I'm sure they look lovely in tunabagel's gifts.
Sheepswool or synthetic (which the shopkeeper will swear blind is either alpaca or a blend) for around Bs40. Look to pay over Bs100 for real alpaca as tunabagel says, although not the best quality at that price (the cheaper alpaca wool is coarser and is the stuff sheared from behind the knee joints etc).
