Oracle 18c

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create table fulldata (year, total) as
          select 2019, '$.00' from dual
union all select 2018, '$.00' from dual
union all select 2017, '$110.00' from dual
union all select 2016, '$.00' from dual
union all select 2015, '$.00' from dual
union all select 2014, '$70.00' from dual
union all select 2013, '$50.00' from dual
union all select 2012, '$50.00' from dual
union all select 2011, '$.00' from dual
union all select 2010, '$.00' from dual;
10 rows affected

select to_number(total, 'L999G999G999D99', 'NLS_NUMERIC_CHARACTERS=''.,'' NLS_CURRENCY=''$''')
from fulldata;

TO_NUMBER(TOTAL,'L999G999G999D99','NLS_NUMERIC_CHARACTERS=''.,''NLS_CURRENCY=''$''')

0

0

110

0

0

70

50

50

0

0

select to_char(avg(
  to_number(total, 'L999G999G999D99', 'NLS_NUMERIC_CHARACTERS=''.,'' NLS_CURRENCY=''$''')), 
                   'L999G999G999D99', 'NLS_NUMERIC_CHARACTERS=''.,'' NLS_CURRENCY=''$''') as level_1
from fulldata;

LEVEL_1

                   $28.00

select to_char(avg(to_number(total, '$999,999,999.99')), '$999,999,999.99') as level_1
from fulldata;

LEVEL_1

          $28.00

select *
from fulldata
where year < extract(year from sysdate)
and year >= extract(year from sysdate) - 5;

YEAR
TOTAL

2018
$.00

2017
$110.00

2016
$.00

2015
$.00

2014
$70.00

select to_char(avg(to_number(total, '$999,999,999.99')), '$999,999,999.99') as level_1
from fulldata
where year < extract(year from sysdate)
and year >= extract(year from sysdate) - 5;

LEVEL_1

          $36.00

select *
from fulldata
where year >= extract(year from sysdate) - 4;

YEAR
TOTAL

2019
$.00

2018
$.00

2017
$110.00

2016
$.00

2015
$.00

select to_char(avg(to_number(total, '$999,999,999.99')), '$999,999,999.99') as level_1
from fulldata
where year >= extract(year from sysdate) - 4;

LEVEL_1

          $22.00