bid or buy

Is it worth it?
I needed a few gems so that I could practice my new gemstone setting skills.
So I went onto bid or buy to see if I could purchase some at a reasonable price.
Of the 4 purchases I made I am only really happy with 1 purchase.
The final straw being a tanzanite I recieved today from TFM.
The stone is definitely not as blue as the photo and there is an obvious chip in the stone.
I realize that I never paid very much for the stone so I could not expect very much. But what would have happened if the bidding for the stone had gone higher would the seller still have sent the defect stone?
Does the seller justify a horrible stone because I never paid very much in the first place?
Was I bidding on this stone all along or do they keep their rejects for cases like this when only one person bids on their products?
In all the cases I checked the sellers ratings and they get brilliant ratings.
Am I expecting too much?
The blue stone I received last week was replaced with 2 citrines - so I believe the guy when he says the first stone was never sent by him - then where did it come from? where did my stone go?
Then in the same parcel was a tourmaline with a chip in it. Can you believe it? Surely if you are fixing up an order that went wrong you wouldnt make a customer even more unhappy by sending them a chipped stone.
Are stones without chips just something that doesnt happen? Why dont these people get bad ratings if this is the kind of thing they are sending out. Is it the same as the blue stone / citrine saga where the guy demands that I change his rating?

An answer to my question came in the form an email from TFM
Good Day

My add clearly stated that the stones are selected from a large group and therefor the quality may differ... I will send you a replacement one free of charge if that is okay with you... I am really trying to achieve 100% positive ratings on bid or buy, so if this appeals to you, please change your rating, i will send the stone this afternoon. Sorry about the inconvenience.

Kind regards.
Rico

I have recently tried bid or buy again and have received two beautiful stones
The first an octogan shaped heliodor from top drawer.
and a beautiful spiderweb turquoise cab from gem zone I am extremely happy with both purchases.
I have decided not to change my rating and told him not to send a new stone.