You talk about ADA, so I assume somewhere in the U.S..
Cheapest gas powered vehicles can be legal, not legal, not legal but no one cares depending on what State.

$120, kit, you provide the pedal bicycle -- https://www.amazon.com/Iglobalbuy-Bicycl... -- not legal on the streets in any State that I know of, but no one cares.

$316 -- https://www.amazon.com/ProGo-PS3000-01-P... -- Propane gas powered stand-on kick scooter. Street legal in California, but you need a driver's license. Totally illegal in NYC, illegal in most States.

$500, plus shipping, tax, DMV fees, etc. -- http://www.superiorpowersports.com/50cc_... -- a cheap Chinese motor scooter (aka MoPed, Scooter, etc. depending on the State)

That is for new. Actual cheapest gas transportation would be a used gas "scooter", such as a Honda Metropolitan, Elite, Yuma, or even a used Chinese scooter. Check your local Craigslist. You will probably need a driver's license, a motorcycle license in California and at least one other State.

Using the Student Ventra Card for non-school trips

Student Ventra Cards can be used for out-of-school riding, too—regular fares are automatically deducted from transit value outside of Student Reduced Fare hours or outside of a school term.

For children 12-20, a regular Full Fare is deducted from transit value.

For more information, you can contact Ventra Customer Service at 1-877-NOW-VENTRA.

Nothing wrong with you getting to work the way you do.

If co workers are wanting to share a ride at least see if it is workable part of the time.

Everyone does not have unlimited transportation budgets.

The shared ride might lead to some social interaction after work.
You chose the method that works best for you most of the time. JUST LIKE THEY DO.
WHY you choose your method is your business and needs no explanation.