The price of a painting isn't simply about how much you'll get to put into your bank account. It's also a reflection of you as an artist, of the perceived value of your work (which isn't necessarily the same as the price tag). A consistent price structure regardless of where a painting is sold reinforces this.
Large variations in price create the impression that your work is discounted, on sale, not worth as much as it was once was. Even, horrors, that you can't sell any of your work and thus are cutting the prices. If a painting is worth X in Gallery Y, then it's worth the same in Gallery Z. How much commission the gallery is taking determines your profit, it should not be the factor that sets the retail price. If you think you're being charged too much commission, see if you can negotiate a better deal or go elsewhere.
Galleries and collectors will find out how much your work was priced at in different venues, as well as look at the prices you've given on your website, and you'd be foolish to think otherwise. A gallery owner will feel you're undercutting them, a collector may feel ripped off; both are likely to be displeased.
Keep your retail prices (wall prices) the same regardless of where you're selling. If you're selling directly, you're doing the work the gallery would be doing -- marketing, administration of the sale, wrapping and shipping -- so don't you think you've earned the commission?
While collectors aren't above liking a bargain, unless you state very clearly that the price is less because the commission is only 25 percent (or whatever), how are they going to know this is why a painting is selling more cheaply than elsewhere? We all know galleries take commission, like we all know that retail prices differ from wholesale, but galleries won't like you publicizing their commission rates because not only is it business information but it creates a gallery vs the artist mentality. Don't undermine your business relationship, but also be sure the gallery is working for its cut!
The exception to setting a consistent price is if you're selling by auction, where variation is to be expected, depending on demand, and the starting price is often nominal.