There are IR (infrared) loop systems under various names. Trackmate is probably the largest of them: https://trackmateracing.com/shop/en/
These require an overhead loop and the transponders need an unobstructed view to the loop, so transponders must be placed carefully.
You can get a setup with the timing system and three transponders for under $300. A MyLaps RC4 system will run you $3,000 with no transponders. You can occasionally pick up used RC4 decoders for $1,500.00.