Firstly, you have to realize that the purpose of a dictionary is to describe the word in such a way that people can understand the object associated with the word. A "sink" must contain the objects being washed or it wouldn't be a sink. The inclusion of "in" is helpful in conveying this and removing it would impact the effectiveness of the definition:
1) a large open container [...] that you use for washing dishes in
2) a large open container [...] that you use for washing dishes
The "large open" modifier implies that you put the dishes into the sink but including "in" makes it much more explicit. Otherwise, you could have a large open container that washes dishes akin to a washboard. While it wouldn't make a whole lot of sense, the dictionary is specifically trying to associate the preposition "in" with "sink" because that is how you use a sink: You put dishes in the sink in order to wash them.
For common, everyday usage you could remove "in" and no one would be confused but this pattern is common in dictionary entries.
A preposition has "a purely local meaning" in a particular context if the pronoun following it can only refer back to the subject. In other words, me is the only pronoun that makes sense after with in the context you cite. It makes no sense to say:
I don't have any money with him.
He doesn't have any money with me.
In such contexts it is not usual to use a reflexive pronoun. Here are further examples:
You have your whole life ahead of you.
She ran out, slamming the door behind her.
The reflexive pronoun is usual, conversely, in contexts in which the subject and prepositional pronoun complement could indeed refer sensibly to different people. For example:
I bought a sweater for her.
She doesn't look after him properly.
In such cases, the preposition does not have a "purely local meaning", and if the subject and prepositional pronoun complement are indeed the same person, then that pronoun is most usually a reflexive:
I bought a sweater for myself.
She doesn't look after herself properly.
Best Answer
With, at, or having would be correct here. But, their meaning is subtly different in each.
With or having means the shares are valued at x.
At means the shares were valued at x when he bought them.
For means the price he paid for them which as WS2 points out in comments might be different from the nominal price.
Note that all of these differences are really subtle, and no one would really be confused if you used them interchangeably.
Of doesn't really work here. It makes it sound like: He is buying 50 shares of a stock called the nominal value of . . .