Selling copies of coats of arms either real or spurious ones (there were a lot made up in the C18th and C19th when the middle classes felt like elevating themselves) is common both on the internet and elsewhere. I know of and have copies of two for my own surname. Both happen to be spurious (never granted by the College of Arms) but even if they were not I would have no right to them. Only the family and their direct descendants have the right 'to bear arms' but then like most people I have acquired them just out of interest and in my case researched the families who made them up in the first place.
However if you are interested and you fulfil certain criteria
'There are no fixed criteria of eligibility for a grant of arms, but such things as awards or honours from the Crown, civil or military commissions, university degrees, professional qualifications, public and charitable services, and eminence or good standing in national or local life, are taken into account.' you can apply to the College of Arms for your own grant of arms. These are the costs
'When the memorial is submitted the fees due upon a grant of arms become payable. Such fees are laid down by Earl Marshal's Warrant. From 1 January 2007 the fees payable upon a personal grant of arms and crest have been £3,800, a similar grant to an impersonal but non-profit making body, £8,275, and to a commercial company, £12,425. Where a grant of a badge or supporters, or the exemplification of a standard is also made a further fee is payable. A special reduced fee of £4,800 has recently been introduced for parish councils, to cover the grant of arms alone (without crest). Those wishing to know further details of the fee structure should contact the officer in waiting at the College of Arms.'Full information here
http://www.college-of-arms.gov.uk/About/08.htm#aRegards
Valda