I can create ebooks-webapps with these attributes:
a) automatically created table-of-contents expands on mouse position.
b) anyone can-refer to ANY part of the text.
c) internal links shows preview of the destination.
I wrote the required programming (https://synagonism.net/dirMcs/dirTchInf/McsTchInf000008.last.html#idOverview)
EXAMPLES:
1) System of National Accounts 2008 (https://synagonism.net/dirMcs/dirStn/dirHitp/HitpStnStd000.last.html#idIndex) (big file)
2) Keynes General Theory of Employment (https://synagonism.net/book/economy/keynes.1936.general-theory.html#idHeader)
3) US-Constitution (https://synagonism.net/law/us/constitution.1992.html#idHeader)
4) my website (synagonism.net) is full of other examples.
cost depends on:
a) functionality wanted.
b) quantity of text.
c) type of text given.