The transponder can be programmed once in the car.
To get in the car on the cheap, buy a blank key that fits your door lock.
Use some magic marker on the edges that are flat but would normally have the saw tooth pattern.
Insert the blank in door lock and twist back and forth to leave impression in the ink, dry erase may be easier to see than Sharpie.
Use a triangle metal file to manually 'cut' the ridges, it's going to take some trial and error, and a vice to hold the key during this filing is helpful.
The more worn your lock is the better this method works.
The transponder to start it can be found much less than dealer prices at some locksmiths.
This method will get you in the car and if you cut careful enough, another 'real' key can be cut from your handiwork.
Where the Governor is on a steak, the cops are on the take, and the welcoming committee is a sawed-off shotgun!