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If you go on eBay, set up an alert for "SRAM TT" and check the email every day. I bought a pair that were £30 buy it now. Also join some Facebook groups for selling bike parts (if you're in the UK there's one called "UK bike parts for sale or free"). If you look at the sold listings on eBay £25-£30 seems to be the best price you're going to get.
Also you could have a look at the classifieds on here, better chance of someone doing you a deal.
I have been waiting for ages for a decently priced 10sp bar-end TT shifter to pop-up anywhere...