To do this without helpers use --SUBSTITUTE()
as the array:
--SUBSTITUTE($A$2:$D$4,"<","")
So to get the average:
=AVERAGE(--SUBSTITUTE($A$2:$D$4,"<",""))
To get the Median:
=MEDIAN(--SUBSTITUTE($A$2:$D$4,"<",""))
By doing this the formulas need to be entered as array formulas. To do so After typing the formula hit Ctrl-Shift-Enter instead of Enter, Tab, or clicking out the cell. If done properly Excel will put {}
around the formula.