Either: Under £20 posted - I'm not bothered about rub, paint etc.
Or:
cheap (chp)
adj. cheap·er, cheap·est
1.
a. Relatively low in cost; inexpensive or comparatively inexpensive.
b. Charging low prices: a cheap restaurant.
2.
a. Obtainable at a low rate of interest. Used especially of money.
b. Devalued, as in buying power: cheap dollars.
3. Achieved with little effort: a cheap victory; cheap laughs.
4. Of or considered of small value: in wartime, when life was cheap.
5. Of poor quality; inferior: a cheap toy.
6. Worthy of no respect; vulgar or contemptible: a cheap gangster.
7. Stingy; miserly.
adv. cheaper, cheapest
Inexpensively: got the new car cheap.
Idioms:
cheap at twice the price
Extremely inexpensive.
on the cheap
By inexpensive means; cheaply: traveled to Europe on the cheap