Cost of a new tube depends on the size, manufacturer, and shipping costs. In general, a new 19" tube sells for around $125 to $150 just for the tube. A 25" tube sells for $175 to $250.
All tube convergence must be re-performed as you must transfer the frame ground strap wiring, degausser coil, yoke, and convergence ring manets over to the new tube. Then everything must be re-aligned.