Airbags are initiated by G-force. If you hit something solid enough, the g-force will set them off. No bumper will prevent that.
Yes, airbags are pretty expensive to have fixed in a certified shop. Alternately àll the parts required are available on CL or oher online sources for reletively low cost. I have seen autos, which had been totaled in a frront end collision, fully restored in a handyman's garage. No insurance claim leaves you with a clean title. No mechanic's bill leaves you with a clean carfax.
