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Are you a

d20 (a 20 sided dice)?

I'm covered in numbers but I do no maths.

d20s have the numbers 1 thru 20 on them

I'm sharp and pointy but I do no harm.

There are many points on a d20, hopefully relatively sharp, not rounded.

I get paid to do what costs me nothing.

you buy d20s to roll, which is free

Some people like me but others may prefer my friends.

some people may prefer a d4, d6, d8, or d10

Title

a d20 is used in D&D to roll for an investigation.

Are you a:

Pair of scenic point pay to view binoculars / telescope?

I am covered in numbers but do no maths:

It has prices for time. And some have heading/pitch numbers for directions of points of interest.

I am sharp and pointy but do no harm:

Telescope definitely points and has sharp focus.

I get paid to do what costs me nothing:

It literally takes money to uncover a/two lens(es) that operate(s) without price or effort.

Some people like me but other may prefer my friends:

Some prefer telescope, others binoculars.

And it takes advantage of one of the hints

The title hint is definitely relevant. "Maybe u should investigate carefully". It lets you investigate distant things more carefully.

Are you a

Roulette table?

I'm covered in numbers but I do no maths.

Both the layout and the wheel are covered in numbers but they are just used as bet indicators, no maths is done with them.

I'm sharp and pointy but I do no harm.

The handle is pointy, but is just used to turn the wheel.

I get paid to do what costs me nothing.

You put money down on the layout, but any payout comes from the casino not the table itself.

Some people like me but others may prefer my friends.

There are lots of other casino games that others may prefer to play.

Are you a

Toll Road

I am covered in numbers but I do no maths.

Most toll roads have their unique identifier number every mile or so.

I am sharp and point but I do no harm.

Some toll roads can have sharp turns and all roads point in a direction

I get paid to do what costs me nothing.

Everyone traveling on a toll road has to pay

Some people like me but others may prefer my friends.

Some like toll roads or convenience, others prefer freeways.

Are you a

Analogue clock / wall clock?

I'm covered in numbers but I do no maths.

This probably needs no explanation

I'm sharp and pointy but I do no harm.

The hands of a clock are somewhat sharp and definitely pointy

I get paid to do what costs me nothing.

Time is indeed money

Some people like me but others may prefer my friends.

Sometimes time is on your side / Some people prefer a wristwatch?

Maybe you're a

PENCIL?

I'm covered in numbers but I do no maths.

As well as writing a lot of numbers, pencils might also have numbers written on themselves, e.g. "3H", "2B", etc. They don't technically do maths, although people can do maths with them.

I'm sharp and pointy but I do no harm.

Pencils are sharp and pointy, but they're not weapons or used for harm.

I get paid to do what costs me nothing.

Writing?

Some people like me but others may prefer my friends.

Some people like to use pencils, but others prefer pens.

Are you a

Note?

I'm covered in numbers but I do no maths.

A note is covered with numbers(its value)

I'm sharp and pointy but I do no harm

I didn't relate this

I get paid to do what costs me nothing.

I got stuck here

Some people like me but others may prefer my friends.

Notes are liked by everyone but their friends (coins).

It even fulfills hint number one

Are you a

Pin?

I'm covered in numbers but I do no maths.

A pin is made up of numbers

I'm sharp and pointy but I do no harm

Alternate use of pin- e.g. a needle

I get paid to do what costs me nothing.

You make deposits or withdrawal money using your pin at an atm

Some people like me but others may prefer my friends.

People choose their own (most often unique) pin numbers

I think that you are

1. Amusement park game, which is usually called somehow like "Hammer" or "King of the hammer" or 2. Compass or 3. Syringe

I'm covered in numbers but I do no maths.

1. This game has numbers which "measure" strenght or 2. Also numbers - degrees. or 3. Numbers are for volume

I'm sharp and pointy but I do no harm.

1,2. And moving pointer which stops on numbers or 3. Literally very sharp; used for treatment, though

I get paid to do what costs me nothing.

1. Coin slot is for quarters or 2. You buy compass; it points north anyway, even if you won't buy it. 3. You buy syringe; all work is done by nurse, though

Some people like me but others may prefer my friends.

1. You have a lot of things in amusement park, you may prefer something else or 2. You may prefer GPS or 3. You can take your medicine/vitamins in a different way.