The 4.5% is an estimate, not a rate we have.
Swansea has not borrowed this money yet. The district’s own page says the final cost “may be higher or lower depending on the actual interest rate and financing terms when the Town completes the borrowing.” Borrowing has been getting more expensive, and every half a point adds roughly $10 million to what taxpayers repay. At 5.5% instead of 4.5%, the 30-year total goes from $162.6 million to $182.2 million.