Depending on the phone, I would think a private shop would be happy to flash your phone for you. Seeing as how they are not permitted to charge for the rom itself according to the GPL, they will charge you for the service (and possibly an sd card, if they give you one.) I've seen pre-loaded sd cards for the Barnes & Noble Nook go for $50. Granted, the Nook is pretty much plug and play, so $50 for a free file and a $5 card is a bit of a rip-off, but if you are asking the shop to perform the service and troubleshoot afterwards if there are problems, then $30~$50 doesn't seem unreasonable.