If you want a $25 plush of a show canon character, try Walmart, Toys R' Us, or Amazon. If you want one of a non-canon character, you're out of luck. While most can agree that prices for plushies can get a bit outrageous, $200 to $700 is perfectly fair for a one of a kind, hand-made item.
Minky, the nice material that a lot of plush artists craft with, starts around $10-$30 per yard, not including tax (or shipping), and can shoot up to three times that amount (or more) for certain colors, patterns, or designs. Unless the character you are having created is one solid color, you are already looking at anywhere from $30 to $100 in just the fabric. Filling can be anywhere from $5 to $15 for simple cotton and poly blends, but can also double or triple in price depending on quality and other factors. Admittedly, a good portion of the eyes are available for free or cheap from some of the fandom's embroiderers, and thread is virtually negligible, you are now left to consider equipment, software, and educational costs. We still aren't even considering actual time spent craft yet either. I've found that the time range for at least some plushie makers is around 10 to 20 hours, depending on complexity and how much time per day they actually have available to craft. At federal minimum wage, that's $72.50 to $145.00, not including any paid breaks, a standard for most jobs.
Just to low ball the entire cost to create, let's say you are commissioning an OC with a solid body color, and a two-tone mane, all three of which are relatively common colors. The artist is really quick and takes only 10 hours to make it and delivers it to you at con, removing shipping costs. We're also going to ignore costs of equipment, etc., since that is hard to quantify and is added later on by the artist to arrive at the final sales cost anyway. The cost to make it would come out to somewhere around $100 to $125, in materials and minimum labor. Just materials is still around $40 to $65.
$25 would cover half the fabric and maybe a handful of cheap cotton filling. Felt, yarn, and other materials won't give you that show style or durability that a plushie requires, but they are still alternatives that I've seen many do wonders with.
(Sorry for the rant, everyone, I'm just rather over-protective of - what used to be - my artists and vendors.I still have a soft spot in my heart - and possibly a soft spot in my head =P - for them. Art is worth so much more than even the artists give themselves credit for. Just because I can't justify spending $300 to $500 on a plushie of my OC right now doesn't mean that the artist isn't justified in charging that much.)