State transportation officials are shelling out nearly $12 million to cover hundreds of incentive-laden packages they gave ex-toll collectors, completing the pricey deal the state cut to eliminate their jobs in the shift to all-electronic tolling.

The payout tab, detailed in data provided upon a Herald request, includes a $10.8 million check MassDOT plans to cut to the state retirement board by June 30 to cover “enhanced” pensions for 117 former toll collectors as part of the state’s agreement to eliminate staffed tollbooths on Interstate 90.

MassDOT officials say they’re choosing to pay the state retirement board in one lump sum before the end of the fiscal year to avoid additional interest payments.

“MassDOT paying this off in a one-time payment in this fiscal year is a measure of fiscal responsibility,” spokesman Patrick Marvin said.

The overall cost of sweeping nearly 500 workers from tollbooths grows to $11.9 million when factoring in additional buyouts and lump-sum payments.

But officials say it actually falls well below the $17.8 million MassDOT had budgeted for buyouts, after fewer workers than expected took the retirement packages, instead opting to take other state jobs.

The payments make up the final tally of an estimated $24 million package the Deval Patrick administration had negotiated with toll workers in 2014, which also included a series of pay bumps spread over the two years.

At the time, state officials argued the extra costs were justified because the state expected to save $50 million a year on the switch to all-electronic tolling.

But the Baker administration said last summer that the estimate was wildly overblown. After an increase in administrative and other costs, the net savings from moving to all-electronic tolling is expected to be just $5 million, according to Tom Tinlin, the state’s highway director, who said the state would see other benefits, like faster travel time.

“Quite frankly, they didn’t factor in the amount of running this program,” Tinlin said last August.

All told, 117 toll collectors got an “enhanced retirement benefit,” which added five years to either their age, years of service or a combination of both when calculating their pensions. But there were dozens of others toll workers who got different deals. They included:

• Twenty-two who took a lump-sum payment equal to 50 percent of a collector’s last year salary, totaling about $742,000;

• Roughly 50 who were laid off, but were eligible for a different stipend of $1,000 for each year they worked, up to $20,000. That cost the state $370,557;

• Another 112 other former toll collectors ultimately stayed on at MassDOT, albeit in different roles. About 180 weren’t eligible for any incentives.

State officials have largely heralded the switch as a success. Fears of highway-choking traffic amid construction never materialized last fall, and construction crews actually finished the first — and likely most disruptive — phase of tollbooth destruction ahead of schedule.