Restaurants in Paris - arc de triumph and Luxembourg gardens

I'm afraid that "reasonable price" and "best restaurants in Paris" don't often occur in the same bed.

You usually get one or the other but not both.

What does "reasonable price" mean to you, in Euro or whatever currency you think in (in Paris it is Euro)?

We liked Bastide Odeon near Luxembourg gardens. Don't remember the price but it was under 100 euros. If you are up for taking the Metro to other locations you will find several well priced restaurants near the Pantheon.

Rue Monsieur le Prince, near Luxembourg Gardens, has a lot of very inexpensive restaurants, mainly Japanese places, as well as the Polidor, which has a large selection from a single plat du jour and a lunch menu during the week to 3-course prix fixe choices.

In general, you should expect traditional restaurants in Paris (compared to cafes and brasseries) to be spendy.
Good food but it comes with a price.

The Bib Gourmands recommendations at viamichelin.com may be helpful, those are the budget recommendations but in Paris I think are 35 euros and under per person, and you may not find too much of the "under 35 euros."

This is if you want a traditional French restaurant, as opposed to other types of food venues.

Near Luxembourg Gardens I like Le Rostand, which is just across the street from the Medici Fountain. Nice outdoor seating area.
On the other side of the park, I like Bread and Roses, bakery, patisserie cafe, 7 Rue de Fleurs, out-of-the way, non-touristy relaxing place for breakfast or lunch.