As others have told you, it is a copy of a Singer 15, and that being in a decent cabinet, and including accessories increases it's value.
A year ago, I was paying $20 for similar sewing machines in a portable box. As everything else has increased in price, $30 for it naked would be reasonable. I see a wide oval plate on the pillar, just below the stitch selector. Does that say DeLuxe? I just paid $25 at Goodwill for a portable that says Remington Sewing Machine, but have not had time to play with it yet. The case it came in is crap, but to be expected of pressed cardboard.
Perhaps Cari can tell you if a copy of the Singer 15 manual would be a good one for this machine.
I have so many machines that I have been walking away from the ones offered, but when I took the top of the case off and saw the beautiful shade of blue, both my husband and I said OHHhhhh, so it came home with us. I bought two rolls of blue sparkle duct tape yesterday to try on the case.
Only you can determine if it is good to sew with.