I'm not they are sold that way, but is it possible to buy a "multi-pack" of dildos? I recognize that as a man my experience differs from yours. However, I am bisexual and I have spent some time (and money) buying myself sex toys that I can use on myself (since my wife doesn't like doing anything other than normal straght sex). I know that for an@l sex, they sell inexpensive "beginners" or "starter" packs with a number of butt plugs to allow people (not just gay men) to work their way up to larger sizes. Once you know what you're comfortable with, you can then spent some real cash on a quality item.
Perhaps you could see if it is possible to get "starter" dildo packs, or maybe just buy a number of inexpensive toys in various sizes to try before spending good money on something you want to use/keep for a long time.

I hope this perspective helps.