You should sell it for as much as you can. If somebody buys it for $25, sell it. If nobody buys it for that price for 8 weeks, try to sell it for $10.
I don't think that $25 is ok, I expect that you spent more than 2 hours on it and I think that for a good piece of art, you should try to get way more than minimum wage. But I will not buy it, so I am not the one to make the price.
The supplies do not count. Nobody cares about supplies when they buy art. The supplies only count when you sell decoration. Decoration is not art.
Sell your painting for whatever you want. If somebody buys it and you still like to paint and sell paintings, you should try to sell one for $400. If that works, try to sell one for $4000. Better make a whole set of paintings and try to sell them all for different prices around $4000, $4200, $3800, $3600, etc.
If that does not work, try again at different prices.
Selling art is an art in itself.