The Low down:
Steel Bars:
4130 Steel
some are Stainless but those are rare since it just isn't as cost effective to use SS
Yer regular Steel tubing will bend or snap rather quickly so unless you are under 6 yrs old don't use regular steel tubing
Cost for the raw material is about the same On Line or from a Local Steel yard BUT the local may not stock it and some places require you purchase the full length 20'. I have several suppliers in the LA Area but only one keeps a decent stock of 4130
Here it is about $100.00 per 20' length of Steer tube and Cross Bar
On Line you do have to pay for the shipping but at least you don't have to buy full lengths and UPS will ship 8' so if you have a friend that wants to go in on it together, it would be cheaper. The Longer the piece you buy the cheaper it gets in the long run.
Simple 3 piece T bars like Rob posted up will be cheaper in the Long run- as you grow or bend a part you can just replace pieces as needed and since there is no Welding, just about anyone can put them together.
Welded T Bars require a welder so you'd have to figger that in to the Total cost. If you can weld then of course it makes it quite affordable but if you have to pay someone locally then that will add $$.
You are looking at roughly $43.00 for Tubing in Standard size bars 24"x24"
( 24" is the length you'll have to purchase since they only sell in foot increments)
Vertx T Bars are $50.00 plus shipping 22"x20" so if you want something taller you'll have to make yer own or find a different vendor.
I don't know all of the sites that have T bars and who has what size
