Yes. When getting price quotes, remember that the least expensive quote will not always cost you the least amount. Shoddy, unlicensed plumbing can come with a high price; leaks that ruin floors and ceilings, life threatening illnesses from polluted water, even destruction and death from explosions caused by improper gas connections.
Unlicensed people can charge less because they might not have the proper insurances and may not file the necessary paperwork. If something goes wrong, you will be the one left with the problem. In addition, building owners can face fines when work is not properly permitted and completed by a licensed plumber.