Transom cracks - WHY.
Yes repairable. But if you are asking, you probably don't have the skills and experience to do that repair yourself. It wont be cheap and needs to be done well.
Tube - could be anything:
Pin prick
Valve
Seam
A seam will probably be hardest to fix and will be a sign of potential risks of other seams going.
Personally - I'd expect $20,000 to buy a water ready RIB, especially if its 25 year old