Help with Previous Month Price formula syntax

RichardJ - So you can use the time "intelligence" function PREVIOUSMONTH like you are using but not sure about using that in a column forumula. Seem like you just need to use something like MTBF

See my article on Mean Time Between Failure (MTBF) which uses EARLIER: http://community.powerbi.com/t5/Community-Blog/Mean-Time-Between-Failure-MTBF-and-Power-BI/ba-p/339586.
The basic pattern is:
Column = 
  VAR __Current = [Value]
  VAR __Previous = MAXX(FILTER('Table','Table'[Date] < EARLIER('Table'[Date])),[Value])
RETURN
  __Current - __Previous

There are other ways. @ me if you need me to take a deeper dive.

You may find this helpful - https://community.powerbi.com/t5/Community-Blog/To-bleep-With-Time-Intelligence/ba-p/1260000

Also, see if my Time Intelligence the Hard Way provides a different way of accomplishing what you are going for.

https://community.powerbi.com/t5/Quick-Measures-Gallery/Time-Intelligence-quot-The-Hard-Way-quot-TITHW/m-p/434008

RichardJ , previousmonth should be used with a date table and create a measure.  Column will not work like this

example

previous month value =  CALCULATE(sum('table'[total hours value]),previousmonth('Date'[Date]))
MTD Sales = CALCULATE(SUM(Sales[Sales Amount]),DATESMTD('Date'[Date]))
last MTD Sales = CALCULATE(SUM(Sales[Sales Amount]),DATESMTD(dateadd('Date'[Date],-1,MONTH)))
last month Sales = CALCULATE(SUM(Sales[Sales Amount]),previousmonth('Date'[Date]))
last MTD (complete) Sales =  CALCULATE(SUM(Sales[Sales Amount]),DATESMTD(ENDOFMONTH(dateadd('Date'[Date],-1,MONTH))))

Power BI — MTD
https://medium.com/@amitchandak.1978/power-bi-mtd-questions-time-intelligence-3-5-64b0b4a4090e

To get the best of the time intelligence function. Make sure you have a date calendar and it has been marked as the date in model view. Also, join it with the date column of your fact/s. Refer :
https://radacad.com/creating-calendar-table-in-power-bi-using-dax-functions
https://www.archerpoint.com/blog/Posts/creating-date-table-power-bi
https://www.sqlbi.com/articles/creating-a-simple-date-table-in-dax/

See if my webinar on Time Intelligence can help: https://community.powerbi.com/t5/Webinars-and-Video-Gallery/PowerBI-Time-Intelligence-Calendar-WTD-YTD-LYTD-Week-Over-Week/m-p/1051626#M184


Appreciate your Kudos.