This post gives a more detailed break down of the junior SMR/CRM positions in the Jobs in British Archaeology series.
You can see the methodology here on how these numbers were collected from job postings. In total 226 job postings are represented here.
Lowest pay offered-
Highest pay offered-
Here is a distribution of starting pay (lowest pay) to give you a better idea of what pay is like for this position-
To figure out what the uppermost pay might be the difference, on average, between individual low pay, as shown above, and highest pay offered was 12.66%. So if you have several years of experience you can assume you will be making 12% more then the lowest pay offered. However there is a range of 6% to 45% over the lowest pay so anticipate some variability in that range.
While the average is 21,000 you can see by the distribution that most of the starting pay is below that, some very low. Even with the 12% boost for lots of experience the majority of people will probably be making less than the average.