Counting in Japanese/how much/money

Counting up to 99,999 is rather simple.
number |place value|one's
so 23456 = 2|10,000|3|1,000|4|100|5|10|6
100 = ひゃく
1,000 = せん (in combination with other numbers)
10,000 = まん (in combination with other numbers)

100,000 = じゅうまん (10+10,000)

1,000,000 = ひゃくまん (100+10,000)

10,000,000 = いっせんまん (1,000 + 10,000)

If you want to do 100,000,000 (that’s 100 million), you’d use the word おく (億).

100,000,000 = いちおく

1,000,000,000 = じゅうおく

10,000,000,000 = ひゃくおく

100,000,000,000 = いっせんおく

There are some exceptions:
when 4 is used a number (not the one's) it is よん
when 7 is used as a number (not the ones) use なな
300 = さんびゃく
600 = ろっぴゃく
800 = はっぴゃく
1,000 = いっせん
8,000 = はっせん
10,000 = いちまん

これ　は　いくら　ですか？　＝　How much is this? or As for this, how much is it?

“yen” is えん (円). Just add えん onto a number, and voilà! You have yourself a price. Let’s look at some examples.

1,000えん = せんえん