Until this summer a local department store used to sell M91/30 round receiver Mosin Nagants on sale for $100 out the door. Since then, their numbers have been dwindling and they never go on sale anymore. You can get one for $120 out the door now.
Surplus Mosin Nagant 7.62x54R ammo is plentiful and cheap. I can buy 440 rounds in a spam can at the department store for $85 on sale. It has copper washed steel casings and is corrosive. You have to clean the rifle after you shoot, but it is no big deal.
Mausers? Well you are moving further upscale with those. You can expect to pay three or four times what you will pay for a common M91/30 Mosin Nagant. Maybe more depending on condition and German markings. No way you are going to get a decent Mauser for less than $100.
I was lucky to get an almost new Yugo M48 Mauser from a friend for $200 because he wanted to thin out his collection. M48s are based on the German K98k design and were made in the 1950s in Yugoslavia using German tooling. They look almost identical to the K98k. My friend threw in over 200 rounds of ammo and lots of brass stripper clips into the deal. I couldn't pass it up. Those kind of deals don't come along very often. It is a great rifle and very accurate. I recommend it if you can save up the cash to pay a little more.