Should the other candidates get a better chance for the job, or should
the best applicant get the position?
The best candidate should always get the position. But remember what the term "best" does and doesn't mean.
For your particular opening, the best candidate might be one who will accept the low salary, can quickly learn the position, and can grow in the company for a long time. (For example, noting in your resume that you currently make much more money at your current job is a red flag to me that you won't be happy for long with a much lower salaried entry-level job.)
Someone with a lot of experience may fill all of those needs. But often someone experienced will eventually chafe at the salary and growth aspects of the role.
If you choose to interview experienced candidates for an entry-level position, you must dig in with questions designed to determine:
- why they are applying for a position for which they are overqualified. (They might want to take it easy until retirement. They might be unable to get a job equal to their experience level for some reason. Or there might be other reasons. You want to find out.)
- if they are in this for the long run, or just until something else happens. (Perhaps they just moved to the area and will settle for this job only until something better comes along. Perhaps they are waiting for the economy to change. Perhaps they are planning and studying for a new career. Or something else might be brewing.)
- if they are truly willing to fill an entry-level role. (They might be okay for a short while, but will they be expecting you to pay them more than an entry-level role would require.)
- If they are truly willing to work for an entry-level salary. (Again, this might be okay for a short while, but they might expect to return to their higher salary soon.)
Once you understand more about the experienced candidate, you can still decide to hire them or not.
Remember, there is a reason you are seeking an entry-level candidate and not someone more seasoned. Just because an experienced candidate comes along doesn't mean they are the best candidate, and that doesn't mean that your original reasons for wanting entry-level go away.
My personal experience tells me that attempting to fill an entry-level position with an experienced individual seldom works out. So I approach such interviews very skeptically. But your mileage may vary.