Why should players who earn more in a week than many people earn in 5 years get a tax-free pay day? The thing is, Giggs' testimonial happened whilst he was still playing - and he had many more years ahead of him. Plenty of United fans would have had plenty of opportunities to see him (unless they only attended Welsh friendlies).
There are more appropriate ways to honour wealthy players, and indeed, managers. Wouldn't it be better to have a Q&A session at CCS with Whittingham where he can give anyone interested a warts 'n' all account of his time at Cardiff? I think that would be far more interesting than seeing a cameo appearance.