Avik
If I were you I would try persuade my seniors/manager to get these books in the office library. If not possible then no option but to spend from own pocket. Its worth in long term.
Other things you may try is frequest visits to used book sellers, you may find yourself lucky if you find some bargain. Check with your seniors they might have in their collection and may be happy to let you borrow! Other option is worth trying is if you find a group of 4/5 colleagues, each one can buy one of those books and share among yourselves. This should be the cheapest and most quickest way to get hands over all the books, depends on the group's mutual understanding though.
I believe there might be prints of some of these books officialy published in India to make it more affordable in local currency. You can try investigating! Few years back I would have taken aback by the foreign exchange prices as my months salary would have been less to buy a book published oveseas. But IMHO as of today the salaries in the consulting sector in India have shot up like anything hence bringing the expenditure in affordable region. Hope you wont disagree on this!
In regards to online transactions, I am no expert to advise, but there seem to be various possible options for the safe payment.
Good Luck,
Siddharth.