15 vs 30 years: same house, different price.

In total interest, yes, dramatically — both because the term is half and because 15-year rates are typically 0.5–0.75% lower. The cost is a much higher required monthly payment.

You get most of the interest savings plus flexibility — you can drop back to the lower required payment if money gets tight. You keep the slightly higher 30-year rate, though.

Roughly 35–45% higher at typical rates, not double — because so much less interest is built into each payment. Compare exact figures above.

It's a cash-flow vs total-cost tradeoff only you can weigh. This page gives you both numbers precisely; the decision is yours.

Much faster — early payments contain far more principal, so the crossover where principal exceeds interest arrives in the first year or two instead of past year 15.