I always found dining table prices way high considering that the dining room is not heavily used and in some cases not necessary. To get a decent dining room with chairs you are going to be looking at paying over $500 at the very least. I would say a DIY dining table can be worth the effort.
Most dining tables should not require plans to do yourself, especially if you are not looking for something fancy. But in order to make an expanding table that looks nice and can serve for years you better follow a plan that’ll save you a lot of trial and error.
If you are interested in doing an expanding dining table yourself, the link below has some nice plans for you to follow.