How cheap are we talking? HD(home depot) has recessed lighting that will cost you about $10 and up per fixture. $14 per fixture including the lamp. What do you mean by "4 springs"? Are you talking about the remodel cans?
I saw some somewhere that had 4 expandable legs or springs that after the can was through the hole the springs popped out and it wouldnt go throught the ceiling tile
Those are called Remodel cans. They are for drywall mostly. You can use the cans that have the two foot expandable bars for drop ceilings as the bars rest on the T-grid. The remodel cans I would not recommend because then the feet would rest on the ceiling grids and they will not handle the weight. Just cut a six inch hole in the grids where you want the lights to be and then set the cans on the T-grid using the bars and position them over the holes.
One thing to be aware of with these remodel cans is that since they are made for ease of installation (i.e. tension mounts) they do not (usually) secure very tightly and may rattle when used in an HT environment. I would suggest a bead of caulk between the edge of the can and drywall to help reduce potential rattles.