i used to work construction and upkeep for high end housing for interior decorating and the such and ive seen huge showers in the middle of rooms or right against walls that were all glass. usually only one side to the wall and the other 3 out usually about 6x6 or 6x10. it might take about $500 more or less to build one probely less if you do it by yourself.
you could mount an air conditioning unit in the growing area, i found a great one at lowes for $150 that has a thermostat on it. Its made for rooms no bigger than 10 -20 square foot or so it would be perfect. lowes also sells a high powerd florecents and their fixtures, they put out like double per tube what reg. tubes do, 6000 or 9000 lumens or something like that. and i had an idea for the glass to put that one way tinting film that is like a mirror on one side, on the glass so that you can see in but the light is reflected back at the plants.
oh and if you have a friend who is a contractor youcan get stuff a lot cheaper, if he or she will let you purchase on their account.
I am just going to use Pvc and that foil coated stirofoam insulation which you can get for some thing like $ 10 for a 10 x 6 ft sheet or some thing like that. then i will put a window unit AC in should only cost me $200 to put in a 10 x 10 room on my outside porch, maybe 300 withthe lights.