FB70 is bebadged linea. To be precise, the FB70 is a Linea in a fibreglass shell that costs about $2000 more than a linea. It was to celebrate 70 years of LM. Just as an FB80 is the 80th anniversary edition of the GB5.
Cost depends on how much work youre willing to do on it yourself....you can buy all the parts from either CP or allpress.