The artist's royalty is calculated as a percentage of the price the record company gets for it (whether gross or net I wouldn't know). Remember that mark-ups put on the price by retailers, and the 17.5% VAT (sales tax) are not part of the equation. Taking all that into account, 48p per unit is probably about the usual rate. Topic Records are not considered exploitative, so far as I know, by those who record for them.