[Plugin: custom tables] Data sorting

I have a table with a column labeled Price, which is the one used for sorting. I use int(11) and the numbers are sort properly but I need to add a thousand separator. How can I achieve this?

Also, when the field is left empty it automatically populate it with a zero. How can I stop this?

All i need is my data be presented in such way like this

[row 1] (empty space)
[row 2] (empty space)
[row 3] 10,000
[row 4] 18,000
[row 5] 23,500
[row 6] 119,000
[row 7] 200,000

Thanks