a phrase to describe a greedy scoundrel, or to name that behaviour

Imagine the following conversation:

B: What's the price?
A: It's fifteen each.
B: Okay, I'll buy it.
A: Too late, now it's twenty each.
B: Why? Because I can afford fifteen?
A: Exactly.

How would you describe A or A's method? A is a scoundrel, his method greedy. Is there a better word for it, or a more precise one?

Such a conversation is not new at all. Perhaps some famous writer made use of it in one of his or her novels, and I can take the name of the character who is a seller.

I am debating a slightly more complicated bargain strategy than the previous example:

B: What's the price?
A: It's fifteen each.
B: Okay, I'll buy a dozen.
A: You can only buy one at this price, the next will be twenty.
B: Why? Because I can afford fifteen?
A: Exactly.
   And I'll keep raising the price to test your bottom line.

As you can imagine, this strategy, or its variants, are employed by some e-commerce websites. It cannot go without a name, but I am not yet in the industry to know its name, and I didn't find it when I googled it. Since I am not specifically addressing e-commerce, I may as well improvise one for the convenience of debate.

Edit: in the end I used the term "Lowball technique" as suggested by the chosen answer.

Solution 1:

By pure luck I came across this term which describes a similar sales technique:
Lowball Technique

An unscrupulous sales technique where customers are initially quoted a lower price, then informed that there has been a mistake and the actual price is higher. Customers who initially agree to pay the lower price are much more likely to continue with the sale at the higher price.

Low-ball

The low-ball is a persuasion and selling technique in which an item or service is offered at a lower price than is actually intended to be charged, after which the price is raised to increase profits.
An explanation for the effect is provided by cognitive dissonance theory. If a person is already enjoying the prospect of an excellent deal and the future benefits of the item or idea, then backing out would create cognitive dissonance, which is prevented by playing down the negative effect of the "extra" costs.

Also, perhaps:
unscrupulous adj. Devoid of scruples; oblivious to or contemptuous of what is right or honorable.

An unscrupulous businessman (for example) is one who will think first and foremost of his own interests and will stop at nothing in order to achieve his aims. In doing so he may employ several tactics which may or may not be legal, but which many would claim are dishonest.

Thus the character's behaviour could be described as being unscrupulous, manipulative and devious.

Some examples from allbusiness.com:

Measures announced to combat unscrupulous landlords
"Local authorities in England are to receive a share of £4 million to tackle rogue landlords, as part of a package of measures announced by the Government to increase the quality of rental properties. The funding, which has been allocated to 23 councils, will help them tackle unscrupulous landlords renting out dangerous, dirty or overcrowded properties."

5 Tips to Avoid Unscrupulous Factoring Companies
"This week I heard a story from an Austin Texas company about the common unscrupulous practice of filing a UCC-1 financing statement against it by a Central Texas based factoring company before they had agreed to do business together."

Solution 2:

Gazumping

Gazumping occurs when a seller (especially of property) accepts an oral offer of the asking price from one potential buyer, but then accepts a higher offer from someone else. It can also refer to the seller raising the asking price at the last minute, after previously orally agreeing to a lower one. In either case, the original buyer is left in the lurch, and either has to offer a higher price or lose the purchase.1 The term gazumping is most commonly used in the UK and Australia, although similar practices can be found in some other jurisdictions.

This is a word that became popular in Britain in the 1970s, and has been used a lot since, especially when house prices are rising sharply.

It means something very particular, and is less common in the United States where land conveyancing laws are different.

Person A puts their house on the market for sale at a particular price. Person B comes along and offers (verbally) the asking price. Now person B does not actually own the house until contracts are signed, and searches are made by lawyers for clear title etc. These legal processes can take several weeks. In the United States, and in Scotland, the time gap between offer and completion is much shorter, (which has both advantages and disadvantages).

If, while the legal processes are in hand Person A finds they could have sold the house for more, he may telephone Person B and tell him or her that if they still want the house that they will have to pay a further £10,000, or something. There is nothing that Person B can do about it if they still want to buy. They are said to have been gazumped!

Solution 3:

The behavior could be characterized as mercenary

(of a person or their behavior) primarily concerned with making money at the expense of ethics:

she’s nothing but a mercenary little gold digger

The term jack up may also be used

to raise the price of something.

The store keeps jacking prices up.

The grocery store jacked up the prices again last night

The scenarios described are fairly aggressive forms of jacking up prices.