prague welcome card
 

Raileurope is offering praque welcome card for $48/per person
Free entry to nearly 30 historic sights, museums and galleries for 4 consecutive days.
72-hour public transport ticket valid on Prague's buses, trams and underground; suburban buses and trains (including Prague funicular railway)
Discounts on sightseeing tours, guided walks, concerts, theaters and music clubs
Free Prague guide
They don't specifiy what museums and such, how expensive are these things in Prague, should I purchase this card?

don't bother, 3 day ticket is worth about 15 USD and includes all mentioned above. And most attractions are free.

the 3 day travel ticket is only of value if you have a child with you,it cost 330czk,24hour tickets cost 100czk and arere the best way to go.
as to the card,unless you intend to visit lots of places then it really isn't worth it.
http://www.praguewelcomecard.com/
most of the entrance fees are fairly low and many are free.St Vitus is usually free for the main area but costs for some areas like the tower,there is a combination ticjket you can buy that cover the whole of the castle complex.
http://www.praguewelcomecard.com/
this website is a very good resourse for you and will give you lots of info.
many walks and tours can be booked online and offer similar discounts to the card.

http://www.prague.net/
sorry wrong link,this is the correct one.
(can we have an edit button please)

Well, the value of the card is about $120. But I find it useless 'cause it's impossible to visit all those places in 4 days. Btw. I'd like to know which agency offers a discount on the sightseeing tours ... I've been in this business for a long time but never seen an offer like that :) ... even if it's a perfect idea and I will check it!