The Hammers are set to sign the Mexican striker, 29, from Bayer Leverkusen in a £13million deal - two years after he left the Premier League.
Lomas thinks the price is a bargain and he's expecting big things once the deal is done.
He told bwin: "You can look at his goal-scoring record wherever he has played and £13m is a snip.
"Even at international level, he's scored nearly 50 goals in less than 100 appearances so he definitely knows where the back of the net is.
"Hernandez is only 29 and he knows the Premier League – for me, clubs have got to be signing these players. If West Ham got someone like Javier Hernandez, it would be a great, great signing."