Which is why you award to the best value tender, not the cheapest. Of course, the challenge comes in setting up the bidding process to ensure you get the best value...
the bidding process will come down to specification which every party tendering for the work will have to meet. it wont be the spec of the equipment that will be poor comparitively as it will be exactly the same as the other submissions as the spec has to be met to qualify for submission.
all public sector tenders are awarded to the lowest bidder, no matter what their track record. there is a certain track record and reputation that a company or individual must meet to get on the list of approved bidders but the lowest bid will get it and we all know why they're the lowest bidder.
i can only assume that the people on the list ( a lot of brown envelopes involved ) are marking up materials by a certain % as they know they will get away with it and the people purchasing couldn't really give a stuff as they've got a generous budget.