Yes, but you have to get a deal on the food to make it worthwhile, or add things to make it more than 'just tomatoes'. For example, how much does a jar of Salsa cost these days (I haven't bought it in about 5 years)? Making salsa or marinara with the tomatoes may be a worthwhile venture if you shop for tomato seconds (slightly blemished or a day or two passed their prime). Farmer Markets in our local area are too high-priced, so we make a leisurely trip out to Amish country (30 min drive) and buy things right from the farms and since they can/preserve, they understand how to price things for bulk purchasing. I grow my own garden, but I will still supplement with 2 - 3 trips out there for things that take a lot of space to grow (melon/pumpkin) or have just been hard for me (broccoli) - I've purchased both broccoli and cantaloupe for .50 each!
Now, you could argue that the gas I spend to get to Amish country cancels out any savings - and you'd be right! But I look at it as providing other benefits: beautiful drive spent with my husband usually spent as an opportunity to discuss "a simplier life", controlling the ingredients with no preservatives, sheer satisfaction of 'I made it', engaging in a culture (Amish) that is very different from me, and canning is a fun hobby!
Also, be sure that you are canning alll the tomato parts - don't throw away any of the juice - can it and make tomato soup or use it as a base for others.