Combining values from different files into one CSV file

file1:  file2:  file3:
1       a       A
2       b       B
3       c       C

~$ paste file{1,2,3} |sed 's/^|$/"/g; s/t/","/g'
"1","a","A"
"2","b","B"
"3","c","C"

file1:  file2:  file3:
1       a       A
2       b       B
3       c       C

~$ paste file{1,2,3} |sed 's/^|$/"/g; s/t/","/g'
"1","a","A"
"2","b","B"
"3","c","C"

file1:  file2:  file3:
1       a       A
2       b       B
3       c       C

~$ paste file{1,2,3} |sed 's/^|$/"/g; s/t/","/g'
"1","a","A"
"2","b","B"
"3","c","C"

file1:  file2:  file3:
1       a       A
2       b       B
3       c       C

~$ paste file{1,2,3} |sed 's/^|$/"/g; s/t/","/g'
"1","a","A"
"2","b","B"
"3","c","C"

~$ paste --delimiter , file{1,2,3}
1,a,A
2,b,B
3,c,C

cat filetwo >> fileone