Sorry, can't recommend anybody in Lausanne because I have mine done elsewhere. If you're stuck you could pick somebody from this list. Alterations are "Retouches". Doesn't take much French to get your pants shortened! "Pourriez-vous raccourcir ces pantalons?" will get the message across!
There's a tailor between the chinese restaurant and the boulangerie Bertrand on St Roch in downtown lausanne. No idea of languages or pricing though. Retouches as others have pointed out is what you need.
I, too, would love this info if anyone has it. Though, cheap and Switzerland don't often go hand in hand. Seems those who provide quality services get paid for it, though there's a certain amount of social justice there I approve of. So, if anyone has a good tailor who charges what he or she is worth...I'd be interested too
If you're looking for a dressmaker there's one on Rue Marterey, just up from Coop Caroline or just down from the Ours metro stop. I don't know the name of the shop, sorry..
I found this thread as I need to get a suit altered (jacket and pants) so I need a tailor rather than "retouches" maybe... I fear it'll be cheaper to buy a new one off the peg than get this done at Swiss prices...
Although they are in Geneva, I use these guys: http://dickandtreems.com/ . You'll initially need to have measurements done at their place, but after that you can order stuff over the stuff and have it delivered to your home or work.
Costs vary depending on the material etc and are about 650CHF for a very good high quality tailor made suit, and about 100CHF for a shirt. I can definitely recommend them.