Here is from one of the most popular theater in Toronto:
General (14-64) $12.75
Child (3-13) $8.99
Senior (65+) $8.99
3D General (14-64) $15.75
3D Child (3-13) $11.99
3D Senior (65+) $11.99
IMAX General (14-64) $18.75
IMAX Child (3-13) $12.99
IMAX Senior (65+) $12.99
UltraAVX 3D General (14-64) $17.75
UltraAVX 3D Child (3-13) $13.99
UltraAVX 3D Senior (65+) $13.99

The theatre I go to is roughly -1 dollar in all these prices. 

Never went but i think my friend said it was around 12 bucks.

Matinee: $6.50
Adult: $8.50
3d: Additional $2.50

I want to say $18.XX, but I'm not 100% sure.

In Cardiff at Cineworld it cost me £7.70 [$12.40] (including the glasses) to watch Transformers 3 3D, but that was on 'Bargain Tuesday' however you do get to keep your glasses for future films saving you 80p [$1.29] each time. For IMAX at The ODEON it is £11 [$17.71] or atleast it was a year and a half ago when I went to see Avatar.

I DESPISE 3D movies.

I really have no special feelings towards them either.  While the 3d works perfectly fine, it just doesn't do that much for 99% of the movie it is incorporated into.  The little it does do often seems to be blatantly made specifically so it will look a little special on 3d.  I generally just don't see the purpose of spending $2.50 more on what I see as very little additional content to a movie.

Really and I thank the heavens that harry potter wasn't in 3D lol (Saw it today, it was awesome!)

It is illegal to charge for glasses in the US (then you could bring your own and they would be required to charge less by law).

Thus, they charge a 3D "tech" fee (usually around $3).

Here in Cary, NC (US) tickets cost me $13:50 for an Adult at night.   Its $10 any other time.  I just got back from HP&TDHp3

3D film generally get booted to the VMAX cinema which could bump the price up to $25.00AUD

Therefore they cost between $18.00 - $28.00 USD