金額の前にはforを入れると思います。
We usually eat lunch for under ten dollars.
これで合ってますか？
ただ、forとunderが続くのが変に見えます。
We usually eat lunch under ten dollars.
こちらの方が良いでしょうか？
Native speakers will say like this: “I usually eat for under 10$”.
There are lots of other ways to say it, but this one is the most accurate and most commonly used.
Here is an example on how to use this:
A: What do you eat for breakfast?
B: I usually eat breakfast for under 10$!
ネイティブスピーカーは以下のように言うでしょう：
I usually eat for under 10$
（私はたいてい10ドル以下で食べます。）
他にも色々な言い方ができますが、これが最も正確で、よく使われます。
これを使った例です：
A： What do you eat for breakfast?
（朝食には何を食べますか？）
B： I usually eat breakfast for under 10$!
（私はたいてい朝食は10ドル以下で食べます！）
My lunch usually costs me no more than ten dollars.
When you 'rarely' do something it means that you do not do it often, and when something is 'usual' or you do something 'usually' it means that you do that thing most of the time.
When something costs you 'no more than ten dollars' it means that it could be any amount up to ten dollars. So this could even be nine dollars.
「rarely」は「めったに（～しない）」という意味です。
「usually」は「たいてい（～する）」という意味です。
「no more than ten dollars」は「10ドル以下」という意味です。10ドル以下のすべての金額が当てはまります。ですから、9ドルの可能性もあります。
I don't like spending more than ten dollars on lunch.
If you were to say "I don't like spending more than ten dollars on lunch" it explains to the other person that your preference is to only spend what you usually do on a meal - which is ten dollars and under.
"I don't like spending more than ten dollars on lunch"
（ランチに10ドルを超える金額は払いたくありません）
ランチには普通10ドル以下しか出さないことを表しています。
I never spend more than $10 on lunch.
Lunch never costs more than $10.
When you 'say' that you never do something it means that the thing that you are talking about will not happen for any reason.
When you also say that you only budget $10 for lunch every day it means that you only allow yourself to spend a maximum of $10 a day for lunch.
【例文】
I never spend more than $10 on lunch.
［訳］昼食に11ドル以上使いません
Lunch never costs more than $10.
［訳］昼食は11ドル以上かけません
"never"は「決して～しない」という意味です。
"I budget only $10 for lunch everyday"は、毎日昼食には11ドル以上は使わないという意味です。
Being frugal is certainly a virtue in many situations. If you use the example sentence, it would be in order to convey the idea that you are careful with money and that lunch may be available at this price.
I almost never spend more than ten dollars on lunch.
When I get lunch, usually I do it for under ten dollars.
The first phrase is the negative way of stating this, and the second phrase is the positive way of stating it. Both mean the same thing, and are standard ways of expressing yourself in American English.
カナダ 
イギリス 
アメリカ合衆国 
