What’s up with R134 prices?

I tried one of the propane "Enviro- something" brands.

My 2000 Dakota puked it back out.

I put 134a back in and it's been "better" but not as cold as new.

Funny, as it actually vented out the high side connector.

I thought it had blown a seal, but after it coughed up all that "refrigerant", the port appeared to be OK.

I can't explain it, but that's what happened.