Welcome to Content Management. 🙂
In general post meta is easy to manipulate, it’s just a key/value store for each post. From your screenshot, however, it seems to be a pretty custom implementation by theme that makes fields individual to it.
You will first have to take apart how exactly theme keeps track of its own fields and if it’s friendly to modification. Another hunch this gives me is that it might not be friendly at all to querying by those values. And as soon as you have prices at some point client will likely want to sort/filter by them.
In a nutshell this is doable, but very specific to theme.
Hundred items isn’t actually that many and editing that amount just might take less time in practice than working out and testing programmatic solution. Some of the more elaborate bulk import/edit problems I encountered in the past were very efficiently solved by “we had interns do it”. 🙂