Extra fileld sorting with Number

http://www.joomlart.com/forums/showthread.php?102005

So I changed it back to a drop-down filed which I would like to have working in alphabetical order to reflect

this
578.00
620.00
648.00
680.00
740.00
820.00
838.00
920.00
980.00
1070.00
1299.00
1799.00

and not this
1070.00
1299.00
1799.00
578.00
620.00
648.00
680.00
740.00
820.00
838.00
920.00
980.00

in the frontend